Just a quick thought. These days you can create a special partition in the first part of your drive and just boot from it. No grub, no config really.
You might want to take a look at EFI and an EFI system partition perhaps?
One idea is perhaps to have more than one device? A tablet at home could be used in some scenarios, the rooted phone for some others. Maybe you have an old device laying around?
+1 for Organic Maps. Create an open streetmap account and contribute - its a game changer for me. Instead of a consumer, you're a contributor. (That goes for all OSM ofc)
Signal