I recently came across a post on the Panic Blog about a Clock In/Out System using iBeacons, iPhones etc.
It looks awesome!
http://www.panic.com/blog/punchclock-fun-with-ibeacons/
Source Code https://github.com/panicinc/PunchClock https://github.com/panicinc/PunchClockServer
Turn your Mac into an iBeacon:
https://github.com/lgaches/BeaconEmitter
iBeacons http://estimote.com (3 for $99)
ZeroPush https://zeropush.com
Another Blog:
https://orchestrate.io/blog/2014/07/14/migrating-panics-punchclock-to-orchestrate/
http://andreamazz.github.io/blog/2014/07/01/fun-with-ibeacon/
Alternatives: