GPS sensors seem to be the latest virility symbol for the major R/C manufacturers. There are a number of manufacturers making these devices (e.g. Jeti, Multiplex, Hitec and Graupner). All of them link to their proprietary telemetry systems to provide the pilot with real time display of height, speed and distance.
Recently, I've been looking at a couple of M-LINK compatible devices, one from Multiplex and the other from SM Modellbau.