GPS seems fairly pedestrian now but my dad had one of the early Garmin models in the 90s and it was a kind of magic back then. Even outside of the actual location info, just seeing this thing in your hand listening to satellites up in space felt incredibly powerful. Later on you could get units compatible with Windows CE and mobile devices and it was easy to see why it would be a killer app on smartphones. It’s sad that the complexity and cleverness is all hidden now.

Take a look at the https://phyphox.org/ app for lower level access to the sensors on Android and iPhones. There is a GPS section that gives you coordinates but unfortunately doesn’t tell you about each satellite. The precision of other phone sensors seems even more amazing.

You could also try https://github.com/barbeau/gpstest if you are looking for something more GPS focused.