This is sort of a pipe dream, but imagine taking an Android smartwatch, disassembling the chassis, adding a larger battery, and embedding it in a threadless headset cap.
GPS tracking, maps in a 1.5" screen, bluetooth reports of speed/cadence from one of those little spoke dealies.
You can do this with a regular Garmin smart watch and a bike mount. It doesn't run Android but that doesn't matter. The problem is that it's really tough to read a map on a small display while riding: a real bike computer with a larger display is far superior if you're going to use it for navigation.
I don't want to make advertisement, but what you describe is what Beeline is selling for bicycle and motor bike. I've not tried it. I don't know how good it works.
That made me think: why dont they make a bike mount for my Suunto watch? (Thx to the HNer that suggested checking Suunto out btw), and well, looks like they do: https://us.suunto.com/products/suunto-bike-mount
Wahoo's GPS units are based on Android. You could pair them with a headset top cap holder, though IMO this is not a super ergonomic location for a bike GPS (in front of the handlebars is better).
GPS tracking, maps in a 1.5" screen, bluetooth reports of speed/cadence from one of those little spoke dealies.