Astronomers at the Politechnico di Torino in Italy are working on a galactic GPS that uses pulsars as beacons for celestial navigation:
Here's the basic idea: Pulsars are neutron stars that spin rapidly and emit a beam of electromagnetic radiation, or radio waves. That beam sweeps over us on the Earth as they rotate. We can effectively use them as galactic lighthouses, since the pulsing rate is so steady—as precise as an atomic clock in some cases.
Using pulsars as a sort of interstellar GPS system is more complex than it seems, though. At the speeds most astronomical objects travel, relativity becomes a factor, making calculations incredibly complex, says MIT's Technology Review.