A proximity access system pairs up and connects to a Bluetooth device you keep with you at all times. This can be a phone, a headset or pretty much anything that you can pair up with your computer.
Then when your computer loses the Bluetooth signal from your device it assumes you have moved away from the machine and locks it up!
When you want to access your computer or mobile, the computer or mobile checks the Bluetooth device is there, and allows access.
Must work on XP, Windows7 and Android.