We have Longitude and Latitude in game visible since day 1, IMO we should have access to GPS only if we are in range of GPS satellites/transmitters.
This would require one new part "GPS module" for GPS satellites, no additional part on vehicle (probe core would solve it with new feature). If your craft is in range of at least 2-3 GPS satellites then you can see Longitude and Latitude. Depends on orbit (range from our craft) of GPS satellites we could have different accuracy (degrees, minutes, seconds).
In career mode it would give us new contracts "cover area X with GPS".
Sometimes GPS module could fail and it would require to be serviced by engineer. Repairs should be possible only from command seat and craft equipped with "spare parts box". This mechanic could be used for lots of new things for example drills could also fail from time to time...