The 406 beacons are also monitoried by low Earth orbiting satellites (LEOSAR). The next generation of monitors are being installed on navigation satellites (GLONASS, GPS and Gallileo), some of which are already in orbit for the MEOSAR system, set for initial operational capability in 2018.
All you want to know about the international Cospas-Sarsat system (Sarsat = Search and Rescue Satellite Aided Tracking, Cospas = equivalent in Russian) is here:
International Cospas-Sarsat Programme