[ Thanks to linuxaria for this link. ]
“This software helps you add a little more security to
your desktop. It does so by detecting one of your bluetooth
devices, most likely your mobile phone, and keeping track of its
distance. If you move away from your computer and the distance is
above a certain level (no measurement in meters is possible) for a
given time, it automatically locks your desktop (or starts any
other shell command you want).”