This might sound like a silly product, but if you've ever left your house, then had to double back thirty minutes later because you were certain you'd left the door unlocked, you'll see the value.
The SureKey is a little cover that slides over your existing key. Inside are an accelerometer and a gyroscope that can detect the motion of a key rotating within a fixed point in space (i.e., a lock). Because this is a very precise motion that is impossible to accidentally duplicate, the SureKey knows for certain if it was last used to lock or unlock the door. A little indicator confirms it.
Enter a caption (optional) Enter a caption (optional) Enter a caption (optional) Enter a caption (optional)
For the super-forgetful, the SureKey can also detect if it's been left inside the lock, and will emit a sound to let you know. (The developers do not specify what the sound is, but I'd like to hear a guy in a Brooklyn accent yelling "Take your keys, dumbass!")
Enter a caption (optional)
It of course requires a battery to operate, but the one it comes with reportedly lasts for five years.
Enter a caption (optional) Enter a caption (optional)
The SureKey has already been successfully Kickstarted. If you want to get in on it, they're going for $19 and there's 19 days left to pledge.