Study build — proves which half of the idea works, and exactly where it hits the wall.
This is the whole UX you described. It works, offline-capable, zero API keys, zero cost.
The button above overrode navigator.geolocation — but only inside this one browser
tab. Below is the live proof of how narrow that blast radius is.
| Who is asking | What they get |
|---|---|
| This tab (patched) | — |
| A second tab of this same site | — |
| Any other website | real GPS — unreachable |
| Life360 / Find My / native apps | real GPS — unreachable |
Enumerates every location-related API this browser exposes, and checks for a write path.