Securitas' Alarm Central
Gives you details of who's connecting to you via Bluetooth? "Yes, Sir, we have a lock. He's DEFINATELY in the same building as you. No, we can't tell you which floor. He probably has a mobile phone in his hand, though... Might look scruffy... You know, like a crook."
I can see the other feature being VERY useful; The 21st century Googling of your own name... "Yes Sir, there is one person attempting to locate you via GPS. You."