By the way, the cheapest RS232 sensor I have found so far is this one:

http://www.weathershop.com/temptrax.htm

$129 + $40 if you want a second probe.

What is silly is they sell fancy wireless weather stations with big displays for half the price:

http://www.weathershop.com/lcm_ws7014u.htm

I guess it is all about volume, can't be too many people out there buying RS232 sensors...