If you happen to arrive at the Makers Local 256 hackerspace in Huntsville, Ala., when no one else is there, you just might have to unlock the place yourself.
The typical image flashing through your mind at this point might be of a key on a keychain. However, the door at the Makers Local 256 doesn't take a normal key. You have to insert an authorized USB storage device to open this door.
The lock is constructed from a Raspberry Pi running a Linux distribution called Raspbian, meant specifically for the Pi. The Relay board is there to drive the Powerbolt deadbolt system when someone successfully authenticates. When you insert a USB device into the Raspberry Pi, a script checks the iSerial number of the device to see if it is in the database as an authenticated user. This method allows the person to fully use the USB storage however they please without affecting their ability to authenticate.
The system the hackerspace is currently using was a joint effort between Jeff Cotten, Justin Richards, and Matt Robinson. They are now adding NFC and RFID capabilities to it. You can read about their build, and how to replicate it on their wiki page.
It all sounds nice but I was a bit concerned about what happens if a power outage occurs. Jeff put my concerns to rest though, assuring me that the Powerbolt has a backup battery so even if the building lost power, you could still use the stock number pad to gain entry. A battery backup for the Raspberry Pi should be on the list of upgrades as well.