My former company Ubisense (which I still hold some equity in) is going to have its indoor location tracking technology featured at the upcoming Location Intelligence conference. I'm looking forward to seeing the latest iteration of the technology, which has come along significantly since I left there in late 2005 to join Intergraph. The technology will feature heavily in the opening "speed networking session", and all conference attendees will be given tags which will track their location throughout the conference. Ubisense uses ultrawideband networking, which is generally accurate to within a foot or so (though that depends on a variety of factors). When I worked in this space, I was really surprised to find out how hard it was to do accurate tracking indoors. The difficulty is that whatever type of sensing technology you use, signals tend to reflect off walls, floors and ceilings, and direct signals are frequently blocked by furniture, people or other obstacles. This means it is very easy to get false readings which can result in serious errors in location calculation.
There are a variety of technologies that people are using to try to tackle the problem. Passive RFID really just measures when a tag is within a given distance of a sensor, so it can be used to track whether someone has entered or left a given room or area of a building, but can't give a more precise location (unless you have a very dense set of readers). WiFi is another option which has a pretty coarse accuracy - typically tens of feet, so not enough to reliably identify which room someone is in, and certainly not accurate enough to measure more specific interactions between people. As I mentioned above, ultrawideband is generally accurate to within a foot or so, which puts it at the higher end of the range in terms of accuracy, with relatively low infrastructure needs compared to other high accuracy solutions like ultrasonic or laser sensors.
For several years now I have been thinking that the precision indoor location tracking market is about to take off, and it hasn't quite done so. But based on some of the signs I am hearing about from my friends at Ubisense, I think it may finally be reaching that point. I will write more about how it all works out at the show next week, and also plan a few more updates on what Ubisense is up to.