Atama Sesame 2

3 This key fob acts as a locking device for a Mac or MacBook. Just walk away with it and your Mac will lock at a defined distance and then unlock when you return. You can set two ranges for locking – whether there should be a time delay in locking your Mac and the method to unlock when you return. It works flawlessly (but is only for newer Macs with Bluetooth 4.0). Sesame can also suspend certain applications (using AppleScript), including pausing iTunes/Spotify and setting your Messenger/Skype status to ‘Away’. Christian Hall

A very convenient security solution and easily configurable from the simple admin panel on your Mac.