We made it so if you check in to Apartm.net on Foursquare the door unlocks. Well, not you. Us. So you can't steal our stuff. We did it with Foursquare's Alpha 2.0 API, a local push notification service, an industrial web-enabled relay device, some speaker wire, and knowing about electricity.
More info to come. Follow us at http://twitter.com/apartmnet/
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