Sun SPOTs are devices designed by Sun to be a general purpose small field device for tracking, sensing, controlling and communicationg with the world.
Sun SPOTs run Java on the metal, a JME CDLC 1.1 comatible JVM. They get their code in a special bytecode format packed in Suites.
Sun SPOTs have built in ZigBee radio, and can be fitted with customized sensor boards and customized communication boards.
GPS: not yet, but done as an experiment. Works only outside, and consumes a lot of power.
The Sun SPOTs do proximity sensing.
Run on car battery or other external power source. Both USB and direct connection to the battery are possible.
SpotWorld, a NetBeans environment allows you to administer and directly deploy, debug and control actual devices or virtual devices.
It will take a while before the SunSPOTs are for sale. Check out Sun SPOT World for updates on this.