Just uploaded another Freeware utility to the Freeware page (strange that - doesn't seem an obvious place now does it ... :)).

Blue Presence is a small utility that monitors for the presence (or lack of) of a Bluetooth device, and can start / stop processes depending on whether it is, or is not, found.

Note: Requires a Bluetooth adapter that supports the Microsoft Bluetooth stack - a lot do, but best bet is to try it and see.