wireless distance sensor project

I am getting started with the wireless distance measurement project. I already have some ideas like using u-controller x-bee interface…but it seems pretty expensive…what could be the possible ideas to measure the distance using two wireless interfaces…

https://forum.sparkfun.com/viewtopic.php?f=14&t=34867

with RF/wireless, and without a $10K budget for TDOA, you can’t measure distance.

You have to try to use GPS, ultrasonics, lasers, or 3 TV cameras and photogrammetry.

It a’int easy.