What are the recent developments in the satellite-based tracking of aircraft?
The German Space Agency (DLR) worked with ESA to track flights from space using ADS-B, the same technology behind flightaware etc.
Some info about it is here

A commercial entity, called Aireon, is planning a global constellation to monitor aircraft that will piggy-back upon the next generation of Iridium satellites. But, unfortunately, the recent setbacks to SpaceX launch capabilities have delayed Aireon's schedule. The first launch of the Iridium-NEXT satellites occurred on Jan 14th 2017 and the entire constellation - providing near global ADS-B coverage - is planned to be complete by mid-2018.

Aside from ADS-B, there is also research going on to track aircraft through their exhaust emissions (something I'm working on right now). Nothing is published about that yet, though.