Voyager Pro for Snow
I have been using one since this past spring. Street and Dirt and now set up on the snow bike. Another buddy I ride with has one as well.
The tracking feature works well and is going to be a big plus along with the radios for this winter.
They are supposed to be working on a firmware update that will let you add custom maps, but no word on a date for that.
What is included is a real good OSM topo and streets/trails map. I don't know yet how it will be for the snowmobile stuff, but you can easily load the trails as a track and follow along them when needed. Most of what we do on the snow bike is off trail, so the thing that will be useful is loading wilderness and non-powered boundaries and perimeter trails for avoiding conflicts and getting back to return trails if you lose tracking for some reason.
The buddy feature for tree well and wayward rider recovery will be really nice too. It is amazing how quick we can get separated...