So I've been using this coin sized rfid chip tucked away in my wallet to get me in and out of HeatSync Labs (the hackerspace from which I hail) at random hours of the day.

Got tired of that and laser cut this simple little keychain. Just cut glue, insert, then glue.

hackaday.com/2012/08/09/southwest-tour-heatsync-labs-in-mesa-arizona