Your smartphone lets you leave your camera and watch at home...and now with ShareKey, it'll replace your keys, too. Especially if you're stuck with something like these keys.

ShareKey is different from the other Bluetooth and WiFi apps and hardware out there. It uses Near Field Communication (NFC) and it's supposed to be the most secure.  Instead of opening an app and hitting a button to lock or unlock a door, you need to physically be at the door -- open the wave, wave your phone in front of the lock, and that's it. You're in.  Think of it as turning your smartphone into a key fob.

Needing to be at the door to unlock means it's safer from hackers. Someone can't just hack into your phone to unlock a door and then steal your 42" flatscreen.

Another cool feature is the ability to add other users and give them restrictions as to when they can unlock doors.  This would be great for dog walkers, the babysitter, or family members crashing at your house for a few days (or you can keep your in-laws out after, say, 8PM).

The app would only be for Android right now. The iPhone 5 does not have an NFC chip, but who's to say the next iPhone(s) won't?

As for hardware costs, it's around $150-200 to replace a lock with a ShareKey lock, but it's bound to become cheaper in the next few years.