Bluetooth Screen Lock is a very useful system security tool. If you use your Mac at work or somewhere where you don't want people to have access to it, you probably lock your screen. You may even do it at home when you go out. This application provides you with an automatic way to lock your screen when you step out. For this, you need a bluetooth device and a Mac with bluetooth. When both your device and the Mac are paired, you can select the device and when it goes out of range or the signal strength goes below a certain level, the application will automatically lock your screen. To regain access to your Mac, you will need your Mac's password. Now, the application has some limitations. One of them is that it can't unlock your Mac when the device comes in range again. This would be a nice feature to have, but I consider it optional. Secondly, you won't be able to lock your screen if you have the Preferences window opened. This is a big deal-breaker for me. One thing is to walk away and have the screen locked automatically, and an entirely different scenario would be to have to check that Preferences isn't opened before leaving. It defies the purpose of the app. I can manually lock the screen in the same time that it takes me to check whether the Preferences app is opened or not.