Mac and iPhone owners can say goodbye to unlocking their computer with a password thanks to the new app Knock. Launching today for $3.99, Knock allows a Mac to be unlocked just by knocking on a paired iPhone. The two devices connect over Bluetooth LE, allowing a phone to automatically detect when it nears a paired computer. Though the knocking effect can also be achieved by waving an iPhone in the air, Knock suggests just tapping on it through your pants' pocket, so you never have to pick up the device.

Though Knock aims to make setup and use extremely simple and streamlined, that can go awry should your devices lose their pairing — in particular, quitting the iPhone app made reestablishing the link a mess. Despite occasional issues, Knock appears to work just fine, picking up on your presence as soon as you approach your computer. Knock also says that passwords are encrypted and won't be transferred to any computer but yours, though you will need a Mac and an iPhone made within the last few years in order to use it.

For as uncomfortable as hitting your several-hundred-dollar smartphone is, Knock sells the idea wonderfully in a quite funny introduction video: