As I posted earlier, I have little doubt that after AF 447 and now MH370 there is a need for a complete re-think on Flight Data Recorders for long range aircraft, with ETOPS sectors, becoming ever longer.
My thoughts on real time FDR transmission through ACARS or other SATCOM is not entirely new but I see the major consideration seems to be cost even though the technology exists. Whilst that cost issue MAY be the case if there was continuous data streaming can any electronics or satcom engineers explain if the technology exists to make a burst of compressed data, lasting only a fraction of a second , say every 30 seconds. Data to include basic flight data, alt. airspeed, hdg, and GPS position. A 30 second interval could at least fix the aircraft to within 5 miles or so at Mach.8. AND even with basic data give an idea of the problem and greatly assist in the recovery of the full FDR and CVR.
A number of unsolved accidents led to the introoduction of FDRs and CVRs (and eventually, I guess, cockpit video recorders) so I have little doubt that, after the AF and MH problems, we WILL get this live data sooner or later.