We have always wanted helmet cams, or something that can mount to the snowmobile itself to record our epic rides. Currently we have some cameras that plug into Archos DVRs. I personally haven't been impressed with the whole setup, the DVR itself is bulky, and over time the audio and video tends to get out of sync.
Recently I've been looking into the offerings of GoPro. Their all-in-one solutions seem like a real winner. I think a great, relativly inexpensive setup would be the Wide HERO with a suction cup mount. With this setup it seems like it would be pretty easy to attach the camera to a helmet, or the hood of a sled from some awesome back-country action. For me, the only disappointing thing is the record times, which are about an hour with a 2GB SD card and about 2 hours with a 4GB card (which they say will eventually be supported with a software update). Battery life is about 3 hours with Lithium batteries and about 2 hours with NiMH.