Client side (may be in firmware or software): GPS above certain elevations or speeds requires a special export license that your smartphone probably doesn't have. An unlicensed device is required to output no fix (but it has to be able to calculate that the parameters are outside the allowed range).
How difficult would it be for someone to work around these restrictions? If I have an unlocked Android phone, would I be able comment out the range check and recompile the gps software?
http://ravtrack.com/GPStracking/cocom-gps-tracking-limits/46...