Why not just modify ELTs
Given the costs of real time telemetry and things like the costs of SAR and FDR Recovery, wouldn't it be simplest to just to refit/redesign fixed aircraft ELTs (vs portable raft beacons) on extended overwater or ETOPS aircraft with automated smoke and pressure triggers? They would automatically transmit in flight in the event of a smoke or pressurization event and could be readily cancelled if the smoke was just a mitt in the oven or the pressurization loss was temporary.
If MA 370 was a fire or depressurization event SAR would have been notified hours earlier, we'd have been looking for the plane while it was still in the air, we'd know it's position more accurately, and in the event there were ever survivors in some other crash they would get quicker medical attention.
It seems like a reasonably cheap and effective solution, one that is much more likely to be acceptable to industry.