

For having a dedicated topo setup I would recommend OSMand. CoMaps/OrganicMaps does contour lines too but you can configure things way more in OSMand and it makes a huge difference. I have both apps so here are screenshots of the same place to compare










You might be able to make an ADSB reciever. It’s transponder signals that power sites like ADSB Exchange
https://www.adsbexchange.com/hardware/