There is a lot of room to improve the ELT. The Frugal Flier link Pontius provided is quite interesting- $559 for a modern 406 MHz ACK Technologies E-04 with GPS input. It's an amazing value, compared to the past. However, compare it with a SPOT beacon, which is about $150, has a built-in GPS and also leaves a breadcrumb trail, in addition to being able to send a distress signal, and other messages. If there is an accident, and the SPOT doesn't send a distress signal, say because it crashed into the S. Indian Ocean, the breadcrumbs would provide a speed, heading, and last known position to search from. Sounds like a transponder, doesn't it? Only it's not limited to areas with secondary radar coverage. Adapting the Personal Locator Beacon technology to avionics could solve a lot of problems.