That is what really got me interested, from a logic perspective you see people doing this so there must be some way to do it, but it cant really be GPS since it does not have the right level of accuracy to be able to see it. My thought was that it would have to be something like compass and so on, at least then you could see which direction your team was in, but would not really be able to tell distance.
Triangulation would not really work, because in all of these scenarios the idea would be for it just to work, use the police SWAT style team as an example - chances are they are not going to have time to set up towers or beacons around the place, then do a raid. They just want to get in their and get it done. I guess you could look at direction AND signal strength, but then that does not really tell you how far away someone is since walls, and so on within an internal environment would potentially affect the measurements.
Id appreciate any other thoughts, it is going to really annoy me not knowing how it could be done (strange i know, but still interested)