I bought this watch and the following with a GPS tracker, because the location of the cellular stations gives an approximate result. And duplicating-gives up to 1 m error. In Russia, a SIM card costs me $ 3 per month. I have 4 ARDUCOPTER 2.8 + 4 GPS Ublox MAX, which are on models with a wingspan of 1.4 meters.They are installed permanently on a vibration coupling.And I just throw a model in my forehead when I fly in an unfamiliar place with large and dense grass and shrubs. One day I lost a model in the tall grass.I searched for 3 days, walked and wiggled sticks...on the 3rd day, the regulator began to beep (the battery ran out) - that's the only way I found it. There are also squeakers when the model is lost (the battery was unfastened on impact on landing and the squeaker turned off, but it was lucky in the visibility zone).