Panic has fun with iBeacons:

With this new technology in-hand, it wasn’t too long before I put together a brand new office In/Out tracker called PunchClock. It uses a combination of a geo-fence and iBeacon tracking, plus a simple Sinatra backend hosted at Heroku. The part that took the longest to fine-tune was figuring out the right combination of polling to provide good location information without draining the battery.

Not only does their internal app look great – it’s also available on GitHub for you to play with.