RF tx Rx question

Hey all,
I need a Radio frequency transmitter and receiver that are small (less than a pound) and low power (small enough to run off a battery for a few hours). I need it to be accurate within 2 feet and up to 8 feet or so. I need the accuracy in terms of time difference of arrival between a transmitter and 2 receivers. Also, I am a digital guy, so I don't know much about analog circuits. If whatever device you suggest had some sort of a digital interface, that would be good.

Thanks

Commercial project, or for a hobby?

Rich

....research project

USE IT
http://hobby_elec.piclist.com/e_pic.htm

Thats not too helpful; I know well how to use PICs. I need a transmitter or receiver that can tell me very exact phase difference (if analog) or very exact timing difference at 2-8feet in range. Anyone have any suggestions?

you want board or just you want to design those ?