Would I be correct to say that the Inmarsat satellite technology that has lead the search to the Indian Ocean has not previously been used to locate a lost aircraft?
No, but calculated positions from satellite handshakes have been compared with known positions of similar aircraft, and other flights of the same aircraft. So it seems quite accurate.
Besides which, if the sounds heard underwater were the recorder beacons, the satellite handshake data is largely academic at this point. The actual impact location was never known very accurately because there's only circumstantial evidence that the final handshake occurred as the aircraft was crashing... it could have continued flying for up to an hour afterwards.