Knock securely unlocks your Mac with two taps on an iPhone

Tired of typing a password on your Mac(s aapl)? With Knock, a new iOS app that launched on Tuesday, you no longer have to. Knock uses Bluetooth LE to securely communicate between your iPhone and your Mac. As the name implies, you simply knock on your phone display two times to sign in to your Mac.

The concept here is that only an iPhone that’s securely paired with a Mac through the corresponding Knock app for OS X can unlock the computer. So even if others have Knock installed on their phones, they won’t be able to unlock your Mac. And since presumably you always have your phone with you, Knock adds an extra element of security: the “something you have” authentication aspect.

Here’s what it looks like:

If you lose your iPhone, or don’t have it handy, you can always sign in to your Mac using the traditional method. And one click in the Knock desktop app will unlink a lost or old iPhone.

Knock works with the iPhone 5S, 5C, 5 4S models and the following Mac computers:

  • 2011 MacBook Air or newer
  • 2012 MacBook Pro or newer
  • 2012 iMac or newer
  • 2011 Mac mini or newer
  • 2013 Mac Pro

Since I have an older iMac, I’m not able to test the product, but it looks pretty slick. And because it uses Bluetooth LE technology, it shouldn’t significantly drain your iPhone battery. In fact, you can use the app to unlock your Mac even when the app is running in the background.

Knock is the brainchild of William Henderson and Jon Schlossberg; both of whom have prior experience in the app and web industries. Henderson created Square’s Wallet app while Schlossberg led the user experience effort at Bonobos.

Knock is available in the iTunes App Store for an introductory price of $3.99. I think that’s reasonable, considering the simplicity it adds to an activity that can take place dozens of times per day.