Kodak Zi8 or gopro HD. they both shoot 1080p 30fps, and 720p 60fps, but they are different style cameras, i have both, and love both. the GoPro can be mounted as a helmet cam, as you know, and in some other crazy, inventive places, but the Kodak is easier to use, doesnt use fisheye, and has a built in USB so it plugs straight into computers, which is very useful.
so its really personal preference for what you like to use your camera for, but both are awesome.