Here's an interesting idea: MDA is working on a Space Infrastructure Servicing (SIS) vehicle, which would essentially act as a travelling gas station for aging satellites. Comms satellites usually die once they run out of fuel for delta V maneuvers that keep them in geosynchronous orbit. The SIS would extend the life of a satellite by sidling up it and transferring fuel directly into its tank.
MDA announced a contract with Intelsat about a year ago to service several of its aging communications satellites, but Intelsat has since withdrawn after MDA failed to secure any more customers. In February, MDA said it was waiting on a contract decision by DARPA before deciding whether to shelve the project.
I think the idea is pretty neat, if not exactly revolutionary. Satellites are incredibly expensive to build, and a life extension of even a few years could have a big payoff, especially because the most expensive part of launching a satellite is paying for the launch vehicle. Plus, longer satellite lives means slower turnover and fewer dead satellites contributing to the growing amount of debris in space.
That said, I think ViviSat might have the better idea - they propose a Mission Extension Vehicle that would dock with a satellite, then use its own fuel to boost the satellite's orbit. This approach has two benefits:
1. Less risk - no need to actually open up the gas tank of the satellite being serviced.
2. Wider market - ViviSat claims the MEV would be able to dock with 90% of the 450 or so geostationary satellites in orbit, whereas the SIS can dock to only 75% that have a certain kind of gas tank. Plus, the MEV would be able to do orbit boosting for nanosats with no propellant system, which would make it possible to keep small satellites with no thrusters going at low orbits (<600 km) for more than a few years. If the service was available at a reasonable price point, THAT could be pretty revolutionary.