Indeed, Android is practically a no-go, because it would also have to have support for a framebuffer over SPI for the screen and that's beyond me.
So if you haven't seen it already, there's a from element14 for the Raspberry Pi. Now the current Control and Display on the GPS build is somewhat limiting with what it can display, so I was thinking that with what you can do with the TouchScreen means we can have a lot more data there.
However, is it straightforward? It doesn't seem so to me, what could I run as software?
There's some portable GPS build for Geocaching, but it seems to be made only for Nokia phones https://www.danielfett.de/internet-und-opensource,software,agtl (it's even designed for small screens! agh!).
So I considered making a HTML page that could work with the sensor(s) and such, which may even work to embed a map (for example chromium can run in kiosk mode as you power on the Pi). Unfortunately we can't get access to the Geocaching.com API (even with a paid account) so cache details still need to be added manually, maybe?
So what're your thoughts/ideas?