Epirbs, ELTs etc...
While I understand the impulse to come up with a solution to the lost airliner problem, adding more portable ELTs isn't it. The more portable ELTs in the field, the more false alerts.
I believe the industry is heading toward an ejectable floating ELT similar to a distress buoy deployed by submarines, but that will take a couple of years worth of regulation, engineering and retrofitting. Even if the industry had started to get serious about this the day after MH370 there would have been no new beacons installed by now.
On mayday calls: what added information do you think the crew could have reasonably transmitted? The only advantage would have been a faster search, but that should have been almost instant anyway.