This is a very interesting idea, bill.

I am not a smartphone owner or user, but I'd be interested in an inexpensive RPi GPS unit, if I could take it with me on a hike, use it to gather data about location, distance traveled, elevation gained and lost, speed of travel etc., then download it at home and view a statistical summary of my hike and view a trace overlaid on some form of topo map that I could access for free on the web.

iow, I don't feel the need to view all that data on the trail, but I am always curious about such data when my hike is over. Up to now I've not wanted to spend any real money to satisfy that idle curiosity, but I'd be willing to pony up maybe $40 or so to gaze lovingly on my hiking accomplishments at home on my PC. I'm not sure anyone could make any profit off such a low price point as a cheapskate like me would be willing to pay, or whether I'd ever try to cobble together my own system out of free software and DIY instructions for constructing the unit, but I like your thinking here.