A friend of mine hired someone to gather data on his cheating wife. A device that looked similar to this was used on her car. $400 for a month of real-time location data. Maybe this has nothing to do with conference this person was attending.
The battery pack on the left, and the tracker on the right were in a magnetic Pelican case attached to the underside of a black Escalade. The sim in the tracker was from some US MVNO that I didn't recognize.
I have a car I don't use very often and often forget where I park it. DX and BangGood have GPS trackers you can buy for $20-40 that you can install a prepaid SIM card in, text message and receive coordinates. Not a bad roll-your-own-LoJack.