Or just continously upload the data to the internet, should be quite feasible these days with satellites everywhere.
What I am interested, is feasibility this: nowadays you can buy sailor lifejackets with personal EPIRB which pings the satellite with your location. I am sure that is a lot of waste weight, but then, Lufthansa is still serving food with steel utensil, so maybe its not as bad.
Also, randomly searching info about black boxes, I've found they have option for 90 day pinger batteries. Perhaps that could've aided MH370 search.
See this for possible alternatives: https://www.bea.aero/uploads/tx_elyextendttnews/flight.data....
That would probably be a bit too much for existing satellite communication systems; while most flights wouldn't need to transmit such a signal most of the time (If a plane went missing over, say, the Midwest, we'd find it!), frequent transmissions from every flight over sea, for instance would probably overload today's networks - meaning you'd need to launch new satellites to provide this service, meaning it would be outrageously expensive, meaning it wouldn't happen.
However, if we relax the requirement to, say, once every five minutes or so, at least you'll have a much better idea of where something went down than 'Probably somewhere in the southern hemisphere.'
Would a GPS coordinate every minute really be such a strain on the systems?
That would mean about 1.5 megabytes per minute, globally. I think the global satellite network is easily up to the task.
Multiple short transmissions are more taxing than a few long ones.