Knock is an application that allows you to use your iPhone to unlock your Mac. Just simply "knock" twice on your iPhone screen, even if it is in your pocket, and instantly your Mac will unlock.
It provides you with a safer and faster alternative to using passwords and thanks to a new technology called Bluetooth Low Energy, Knock can securely communicate with your Mac without draining your iPhone battery.
Knock is compatible with all newer Mac models including: the MacBook Air, MacBook Pro, iMac, Mac Mini and the Mac Pro. You will also need an iPhone 4S or newer.
Please note that you will also need to download the accompanying app for your iPhone, which can be purchased via the App Store.