Bushnell offers a device that shows your GPS Located position overlayed on top of satellite and/or aerial photos, much like Google Earth, and does let you see every bush,log and creek, in near pseudo real time.
It works off of the XM Satellite signal. Reception of that signal is spotty at best in Alaska, although I heard you can receive it when you are at elevation as the Satellites are equatorial.
If a devices memory were such that it could hold a certain areas' imagery, it would be no tough task to correlate those images with your GPS's coordinates, and then overlay your "dot" (you) on an actual image.
This can be done easily enough with a laptop, a GPS, a usb cable, and the right software., But it's hard to find a good laptop mount for the sleds handlebars.
http://images.google.com/imgres?img...ox-a&rls=org.mozilla:en-US:official&sa=N&um=1
PS It looks like this unit will do as you'd wish, you can download sattelite/aerial images into it (for a fee) and then display your NAV aids over it. Sweet! The XM part is still true, you would need XM reception to get NEXRAD Weather overlays.