The target of SPOT is
Sun has been very successful in spreading Java to over 6 billion devices throughout the world. Well over a billion cell phones run Java. We in Sun Labs are interested in what comes next. In order to help make sure that the next generation of gadgets is based Sun technology, we developed Sun Small Programable Object Technology (SPOT)
If you are interested you can order a development kit for 299$ and you will get two SUN Spots and a base station. Bot devices with processor, radio, sensor board and battery and the base station only with processor and radio.
Here the parameters of the device:
180MHz 32-bit ARM920T core processor
2.4GHz radio with an integrated antenna
But if you only want to write software without getting in touch with the hardware you can try to use the emulator (read this pdf)
The API and some tutorials are available at this site. So if you are interested in programming a PDA like device download the SDK and the emulator and go ahead...
For more appetizers take a look at this site (some movies about SPOT at youtube).
I hope this was enough to start you up ;-)