After downloading the Knock app for iOS and the accompanying app for the Mac, an iPhone can unlock a connected Mac with two knocks on the back of the iPhone. The iOS app pairs specifically with the Mac app, which creates a secure connection between the two, and the process does not require opening the Knock app.
Faster and safer than typing a password, for iOS and Mac.Because it uses Low Energy Bluetooth 4.0, Knock is compatible with the iPhone 4s or newer, along with the 2011 MacBook Air or newer, the 2012 MacBook Pro or newer, the 2012 iMac or newer, the 2011 Mac mini or newer and the 2013 Mac Pro.
You keep your iPhone with you all the time. Now you can use it as a password. You never have to open the app— just knock on your phone twice, even when it's in your pocket, and you're in.
Using Knock won't drain your iPhone's battery, even if you use it all day every day. Knock securely communicates with your Mac using Bluetooth Low Energy, a new technology that draws very little power.
Knock for iOS can be downloaded from the App Store for $3.99 [Direct Link]. The accompanying Mac app can be downloaded from the Knock website for free.