Bluetooth has become quite popular for tracking -- it's used by , , and more -- but thus far has been limited by its mutually exclusive abilities to sense how close something is or where it reports it is.
With the latest update to the specification (here's a PDF with more detailed information), announced Monday, Bluetooth combines the abilities to allow for a device to sense the direction the signal's coming from, increasing its accuracy and usability.
The Bluetooth SIG, the group that develops the specification, says this system improves down to "centimeter-level location accuracy."
Basically, rather than a single antenna on the transmitter or receiver (depending on application), one Bluetooth device has an array of antennas. By measuring the strength of the signals on each antenna in the array, the other device can determine which is strongest and thereby obtain a direction vector.
Of course, you'll have to wait for manufacturers to build it into stuff you can buy.