TAOS was peculiarly crazy and brilliant. It was written in a sort of macro assembler, essentially a form of assembler with a large number of registers, which was "compiled" to the target platform on demand. It was network transparent so nodes on the network could use devices from other nodes. There's a lot more from an ex-employee here: https://news.ycombinator.com/item?id=9806607

I wish one day that it gets open sourced (but I'd settle for a non-open read-only license) because it's unlike anything else.