These were Sun microcontrollers that run Squawk Java ME directly on metal with gc and all the bells and whistles, created by Sun Microsystems in 2005.
The feature mesh networking and tcp/ip and multitasking. Even the drivers are java just like Java OS.
They run a command and control server by default and there’s graphical network builders and deployment managers (Solarium) they also do some more esoteric stuff like process migration.
↫ Penny
I have no use for these but I want them. They would’ve made an excellent addition to my Sun article. There’s still a detailed tutorial and informational website up about these things, too.

Thom, you are in luck.
At least if you want to do Java based IoT programming in a standard way. Of course it is NOT SPOT, they have been obsolete. But similar hardware is very easy (and cheap) to get today.
STM32, especially some variants, like STM32WB will come with a similar ARM core, BLE (modern bluetooth) and zigbee as SPOT. So will handle most tasks for automation.
For acceleromater… You need to get a “shield”
Or you can get ESP32, which usually comes more “packaged” (there are $10-ish devices with come with extra RAM, mini-OLED screen, some hardware button, etc)
Software?
SPOT SDK is gone, but embedded Java MicroEJ is here
But… I would really suggest looking at Python instead. MicroPython is awesome
(I have a “CARDputer”
https://shop.m5stack.com/products/m5stack-cardputer-adv-version-esp32-s3 (mine is the original, they now have “Advanced”). It is the awesomest geek device. Portable python on the go with a functioning keyboard and interpreter