@KE7GKP, thank you for your good words!
I've been thinking about a short-range range finder between two arduino systems, how could we do that easily? Using radio signal strength does not seem useful, it is too wild a variable, depends on how you hold it, antenna position, etc. Too many factors I think.
What about hacking an ultrasonic range finder, for example. http://www.cutedigi.com/product_info.php?products_id=4281
I notice that the above cited board has an ATMega on it, so if you might be able to get schematics and code. Probably can source an ultrasonic tx and rx from many other places as well, probably on the order of $5 in parts. Instead of pinging the output and reading the reflections on the input of one sensor, split the sensor with transmitter only on one system, rcv only on other. Used in this way, narrowness of beam might not be a problem either. I can synch two RD-11s by radio to within about 10 us, so you could get a common time reference to determine the time between send pulse and receive pulse and thereby distance. Sound is about 1 ft per millisecond, so there is way more then enuf time (1000 us per foot) to sense time between ping and its receipt. a 10 us loop with 10us time sync, puts us at say plus or minus 25 us, that is 1/40 of a ms, so should have something like 1/40 foot or better than an inch resolution. Add fudge, easily 1 inch resolution to a few feet or more.
Just a thought, would definitely require some hacking and experimenting!