It's called Automatic Dependent Surveillance Contract - ADS-C
It is and has been used extensively in Australian airspace for a number of years. It entails the aircraft establishing a "contract" with the ATC centre through a satellite link - aircraft downloads positional and other info at the contract rate. This is usually 30 minutes but can be varied by the controller with jurisdiction - in fact he can "one shot" a position at any time and can increase the rate in case of emergency. In between downloads, the position is extrapolated by the ATC equipment.
The procedure is being trialled of setting the default contract to 15 minutes.
The give-away is the "Dependent" bit - can still be turned off in the cockpit and bingo the aircraft's real position is purely supposition.