A contrived/silly demo app that shows how disk buffering should work.
It's less about navigation, but it shows fake distance, fake elevation, and allows the user to choose one of 3 current dispositions as often as they'd like.
The idea was to have one timer that auto-updates the elevation a random-ish amount, so that it looks like they're moving around, maybe 2 times a second. Similarly, another timer would move around the distance, probably also 2 times a second or so.
Then, another timer would trigger every 10 seconds and report the two values (elevation, distance) within a span or event.
The disposition buttons would generate an event immediately.