That's a pretty common application when you need to synchronize clocks to microsecond accuracy or to a second accuracy but have neither a stable network connection nor a time broadcast (like the German DCF77). It's also used to replace Cesium clocks in cell base stations or for the precision timing protocol (IEEE 1588) for PWE3 networks.

Iep, is there a lot of systems depending on GPS and a major system failure will bring us some chaos.