If you've ever wanted to magically unlock a door with a quick tap on your wrist, this DIY project is for you. Using an RFduino and some special door components, Marc Jensen, James Squires and Shawn Roske at Make came up with an interesting use of the Apple Watch.
Once you have the door module set up, and you have the app configured on your iPhone and Apple Watch, you can unlock that door with nothing but a tap. The downside, of course, is that you have to own an Apple Watch to make use of this build. If you have one, however, and you're chomping at the bit for something to do with it, this might be perfect for you. The concept is similar to past project of theirs, but it incorporates the watch and streamlines things a little bit. You can find complete instructions at the link below.