The most popular and widely promoted helmet camera as of 2011 is the GoPro HD Helmet Hero. I own one, and I am reasonably satisfied with it.

The Helmet Hero is self-contained, smaller than a pack of cigarettes, larger than a matchbox. In use, it is enclosed in a transparent plastic shell with a mounting bracket on the bottom. The camera is sold with two backs for the shell: one is waterproof and the other has openings at the rear to allow better audio pickup.

Thanks to its simplicity and ruggedness, I can give the GoPro very high marks for reliability in use. I have mounted it on a helmet, and also on the rear rack of an unsuspended bicycle, and never lost a shot due to interrupted electrical contact or any other result of vibration.

The best mounting for a bicycle helmet is the supplied helmet-platform and-straps mounting. The platform, on the outside of the helmet, is cinched up tight by means of straps that pass through the helmet's ventilating holes. This mounting is intended for a center-vent helmet, though it can be used with a center-ridge helmet by twisting one strap past the other. There is a pivot in the mounting bracket, so the camera's position on the helmet is not critical. The camera adds noticeable weight to the helmet, more than with "lipstick" cameras.

The mounting hardware looks less secure than it is: I have reports of its being trouble-free for more than two years, yet if the one plastic bracket on the shell, or mating part, cracks, you could lose the camera.

Adhesive pad mounts are sold too with the Helmet Hero. I would use one on a car dashboard when the worst calamity would be the camera's falling to the floor of the car. There is no mounting point on the outside of the shell for a tether. With my old Helmetcameras.com cameras, I can use the cable to the separate recording device as a security tether, by routing it under one of my helmet straps.

The GoPro's ultra wide-angle fisheye lens is excellent, sharp out to the corners and multi-coated. Color is vivid, too. Like other helmet cameras, this is a single-purpose camera, with fixed focus (not an issue with the extreme wide angle lens, unless you would like to take extreme close-ups) and automatic exposure control that can be set either to full-screen of spot model. The Helmet Hero offers five video shooting modes, from WVGA 480 x 848 up through 1080 x 1920 full HD. There is no standard VGA mode, though downsampling and cropping in post production are, of course possible. The Helmet Hero also can take 5 MP still photos and has a self-timer and sequence timer.

The internal battery and supplied 16GB SDHC memory chip are good for three hours of shooting at the highest resolution. You may use a higher-capacity chip if you wish. The battery is field-replaceable, so you can carry a spare battery. The camera may be operated off external power through its USB port, and may also output video, The analog video and USB ports are on the side of the camera, only accessible if it is outside the shell, or if you make holes in the shell, so it will no longer be waterproof.

Adjusting viewing angle is cut-and-try, even if the camera is within sight -- there is no viewfinder unless you buy an optional viewscreen back. Generally, the camera should be tilted down about 10 degrees when using it on a bicycle, so as to get more road than sky in the picture. When the camera is mounted on a helmet, you might use a mirror so you can view yourself in profile, to align the camera -- or ask a companion to help, or carefully lift the helmet off your head without tilting it to check the angle.

The front of the shell has a domed glass window which protects the camera's lens. GoPro calls the window a "lens", but it really is only a window, except underwater, where its curvature puts images slightly out of focus. The manufacturer has announced but not yet released a flat-pane window for the shell that will avoid this problem. The window is of optical quality but not optically coated, resulting in additional lens flare when a bright light source (typically the sun) is in front of the camera.

Audio is mono, of mediocre quality. You will need to use a separate recorder to get good stereo or surround-sound audio, and you will have to synchronize the audio in post production. I do this with a hand clap visible to the camera. I clap again at the end of longer shots in case I may need to correct for timing drift.

Controls are with only two buttons on the camera itself, to minimize the number of openings in the shell. The control sequence requires memorization and viewing cryptic codes in a window on the front of the camera. Setup for different modes is slow, and you must remove the camera from the helmet, or remove the helmet, to view the settings and switch modes.

The camera may be left on, with a start-stop button for shooting, but also there is an "on-off" mode which shuts the camera down completely between shots, sparing the battery. Shooting is then controlled by the on-off switch on the front of the camera. It takes a couple of seconds in "on/off" mode for the camera to stabilize and adjust its exposure. In this mode, your finger will probably be visible at the side of the image as you press the on-off button to start and stop the camera. The camera beeps to indicate stating and stopping, a useful feature when it is mounted out of site but within reach.

A number of accessories has been introduced offered as as the camera has become popular and users have demanded additional features. One already mentioned is the viewscreen, available as an accessory back for the shell.

Another accessory back is buoyant so the camera will float (duh!). GoPro also offers a shell for two Helmet Hero cameras side by side, with a linking connector for synchronized 3-D shooting. This gets into some real money, and requires a very fast computer to process the data. As of this writing, GoPro offers only Windows software for this purpose.

A wide range of mounting accessories is available to mount the Helmet Hero's shell -- with a chest strap; to a standard tripod threading; to a car dashboard, and so forth. These are sold as a kit with lots of little pieces, in a cardboard box rather than, as would be better, a foam-lined case with a place for each piece.

Some GoPro mounting hardware including the helmet strap mount has quick-release snap-in clips. The tripod mount has none, but separate tripod quick releases are sold at camera stores. When I mount my Helmet Hero on a bicycle rack, I use one of these with a bolt-on tripod top, and leave the top part of the quick release attached to the camera -- which still fits into a small belt pouch. It would be nice if the camera itself had a tripod fitting for more convenience of access to connectors, better audio quality and less lens flare when using it without the shell. It shouldn't be too hard for a do-it-yourselfer to cobble up a bracket for this purpose.

To accommodate the camera's extreme wide-angle lens, the window protrudes from the front of the shell, and so it is vulnerable to scratching if the shell falls on its front. Replacements are available at a moderate price. The camera's lens also protrudes, and so it is vulnerable when the camera is out of its shell. Lay the camera on its back, preferably on a plush surface.

You must open the shell to connect the camera to a USB cable to charge the battery or download data; or you may download data by removing the SD memory chip from the camera and placing it into a card reader. This is faster, and the speed is helpful considering the huge files which the Helmet Hero produces. Files are in MP4 format, which can be read by most serious video editing software packages, though they must be converted to .AVI format for processing using the very useful VirtualDub freeware, in Windows. (VirtualDub is not a full-featured video editor, but it offers a very convenient and quick way to perform a number of useful tasks such as splitting up video files. VirtualDub is the platform for Deshaker, superb image stabilization software which is freeware.)

The Helmet Hero's shell and possibly the camera itself would be damaged in a serious impact to the helmet, and there is also the possibility of injury due to head rotation or compression of the camera against the helmet, probably greater than with other helmet cameras that have a smaller profile. The GoPro is very obvious when mounted on a helmet, giving a "Teletubby" appearance to the user. This may contribute somewhat to the GoPro's commercial success, because unlike the others, it advertises itself in use. The obviousness can be both an advantage and a disadvantage depending on whether you want people to know that they are being recorded. Other helmet cameras, including the self-contained Contour, are smaller and can easily be mistaken for head-mounted LED bicycle lights.

I've already complained about the packaging of accessories. The packaging of the Helmet Hero camera itself is as bad if not worse. It is sold in a hard, transparent plastic jewel case, about 5 inches (12.5 cm) on a side, taped to the top of a cardboard box which holds cables and mounting hardware -- a display case, designed for the sales counter. You tear off the cardboard, and then all you have left is the breakable plastic case. The manufacturer does not offer any transport case, as far as I know -- a remarkable omission in a camera designed for rugged use, and which comes stock with a number of small accessories. The owner must cobble a transport case up.

User instructions are provided in several languages, on separate sheets, and you really need these instructions with you to get through the menus. The sheets all look the same until you unfold them. It's a good thing that I can read Spanish!

There is (as of summer 2011) a glut of Helmet Hero accessories at brick-and-mortar camera stores, apparently because the manufacturer prefers to sell the camera through the more profitable direct mail-order channel. So, you may be able to get accessories at a reduced price through a camera shop. I know for a fact that Newtonville Camera, in Newton, Massachusetts, would like to unload GoPro accessories, and also sells by mail order. Sheldon once worked there, before Harris Cyclery -- worth checking!