As you probably know, the Unity notification area (systray) whitelist is no longer available in Ubuntu 13.04+ (so that includes Ubuntu 14.04 and 14.10) so you can't whitelist applications to be able to use the systray. If you can't live without an application that still uses the old notification area, here's how to get the Unity systray whitelist back in Ubuntu (Unity).

You can configure the proximity distance (this is just an approximation because the signal strength is not always the same) and duration and when you move away from your computer, the screensaver is triggered and your computer is locked. When the bluetooth device (phone) is in range, it automatically unlocks the computer, without requiring any input on your side. This is useful for instance if you use Linux at work and want your computer to lock automatically when you leave for a few minutes, etc.