I bought a pair of these gizmos so they could speak among themselves. A JeeNode is basically a barebones Arduino-like microcontroller with an integrated radio for serial or packet communications. They work on a number of bands like 433mHz and 916mHz and others using RF12. You can program them through an FTDI to USB cable and the Arduino IDE.
A pair of completed JeeNodes
They come as a kit so you have to build it. The kit was straightforward and contained very few parts. Some of the soldering was delicate, especially when mounting the radio daughterboard. It’s smaller than a postage stamp by half at least so a steady hand and a very fine soldering tip is needed for the surface work. The rest is a walk in the park. Both of mine lit up and worked right off the bat, although I only have one FTDI cable and so could not test them together. But all of their diagnostics work and report the results shown in the assembly documentation. Like many kits these days, the instructions for the JeeNode were online.
The board is so very simplistic that I figure it would be most easily used as an add-on to an Arduino with greater resources as a means of communication like an xBee or FM radio. To try to use the JeeNode itself as a standalone is certainly doable, but the setup would be more valuable as an inexpensive serial comm setup.
I got my JeeNodes from Modern Device for $22.50.