If the goal is to implement a solution that can help us locate an aircraft to within a 10-15 mile radius, a very simple solution could be to use the HF radio and have it automatically broadcast a Lat/Long position over some chosen frequency whenever an "emergency" conditon is sensed or when the crew press a "panic" button of some sort. The broadcast can be digital if it can be achieved (don't know to be honest), but even an audible message played continuosly over a frequency which a handful of worldwide stations are tuned into would suffice. Broadcasting and receiving the HF message is free of charge and already included in the subscription and you'd have a very good chance of being heard even a 1,000 miles away (given the right conditions). Minimal technology involved. We'd be doing what the crew would do if they had the time, nothing more required IMHO.