Okay, this is pretty interesting-maybe not too practical for the mountains, but interesting.
This video shows a concept of an all electric powered snowmobile weighing in at under 100kg. It's a students' degree project. Check out www.huskydesign.co.uk.
A couple of things to do when you watch this:
1 - Turn the freakin' music off. It's brutally annoying.
2 - Read the comments at the bottom of the YouTube video.