What is the appropriate wireless positional, tracking, and identification technology?

I am just starting to investigate various technologies in the realm of wireless, RFID, IR, laser, motion detection, etc. and was hoping
someone might be able to offer some insight and point me in the right direction.
Generally what I'm looking to do is have various objects, each of which must be uniquely identifiable (via RFID, I suppose). I need to be able to track these objects as they move throughout a room. In addition to knowing each object's location/position, I need to know the distance of a given moving object from other fixed objects in the room as well as distances between the moving objects themselves. As objects approach some distance threshold of another moving or fixed object, some event needs to be triggered (along the lines of motion detection).
The resolution of distance needs to be measurable within an inch or so ideally, and I'd like to be able to configure the distance threshold dynamically as needed possibly configuring different sets of distance triggering thresholds depending on the object. I also need to be able to determine positional changes in elevation as well as laterally. The refresh rate for updating an object's location/distance should be relatively quick, but does not require absolute "real-time" updates. Again, if the refresh rate could be configured, that would be a plus as well.
My questions are many at this point as I'm just starting to investigate the various technologies that seem to offer some possibilities. To start, I'd like to know what technologies or combination of technologies wireless, IR, RFID, laser, ultrasonic, others, etc are best suited to allow me to do what I'm attempting. From what I've been reading, Active RFID tagging appears to offer much of what I want to do, although I'm not sure of it's capability in determining more precise location/position information of tagged objects, and particularly elevation changes.
Also, for the applicable technologies, what hardware is available/necessary to interface with a PC? And are there any software applications and/or development technologies that aid in interfacing with these devices and monitoring any activity/changes in distances/position, etc. I'm somewhat less concerned about the software at this point as I could custom develop something as needed, once I know what I'm trying to interface with.
One of my primary concerns is cost. I'd like to have a solution that is relatively inexpensive as there will be many objects that would need identification and tracking.
Any information or direction anyone can provide would be greatly appreciated. Thanks in advance for your comments.
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