sbright33:
I don't think it uses GPS at all. I believe it has to do with the timing or phase of 2 antennas.
There is an obvious antenna on the base unit which can only be used to communicate with the transponder. There is only one antenna and it looks like a non-directional antenna so I don't think there is any clever radio direction finding going on. This comment on the kickstarter page "Hey everyone- we designed SOLOSHOT with outdoor use in mind- the technology involved doesn't allow for indoor use." plus the fact you are recommended to be at least 50 meters away from the camera leave me certain that the system is based on GPS. I believe the transponder is essentially a GPS receiver plus radio transmitter and the base unit is a radio receiver, GPS receiver and compass.