I have built some arduino-based variometers for soaring model gliders. The idea is to be able to somehow sense the on-board variometer signals on the ground, in order to center the glider in thermals. With no vario feed-back it can be very difficult to judge vertical speed from a distance, especially when flying directly overhead. You can read about the construction of three tested versions and download the sketches here: https://sites.google.com/site/xnebmisc/home .
The first version used the Pro Mini board with the VTI SCP1000 barometer/pressure sensor and a pair of PMR radios. It worked very well as such, but the radio transmission didn't, unfortunately.
For the second version I used an Ardweeny board (which is also pretty minimal in size and weight) and the Bosch BMP085. This time I tried a cheap 433MHz radio which was a dispointment in terms af radio range.
The third and present version works great, I am glad to say! It uses the Pro Mini 3.3V/8MHz and the BMP085 combined with an XBee Pro system. Also I added a SpeakJet synthetic voice chip to the receiver circuit, which spells out the altitude of the model! I have not tested the ultimate line-of-sight radio range yet, but it certainly functions well so far when soaring thermals up to a circa 300 m above ground.