We live in an age where the seemingly mundane task of entering a password can become cumbersome enough for some to compel them to develop an app that helps you bypass that altogether. Knock, for instance, is software that lets you unlock your Mac just by tapping on your iPhone twice. The app doesn’t even need to be running. Think of this scenario: you’re at a cafe, you leave to go to the restroom and lock your Mac, while keeping your phone in your pocket. As soon as you’re coming back to your laptop just tap twice on your pocket and it’ll be ready for you to use before you’ve even sat down, no need to enter any password. It works brilliantly; I just downloaded and tested. The app uses low-power Bluetooth 4.0, so it won’t drain your battery. It will, however, cost you $4 to own. The Mac application is free, it’s the related one on the iPhone that costs.