Well, to be more precise, the system I am about to show you is called B-right/V release 4.5 from 2006. It is an implementation of BTRON, Business TRON specification. You can think about it this way: FreeBSD is a UNIX system. Bright/V is a TRON system.
TRON, or The Real-time Operating system Nucleus, began as an open architecture project by Japanese professor Ken Sakamura in 1984. There are multiple sub-projects, including ITRON for electronics and cars, BTRON for desktops and PDAs, CTRON for telecoms, and many more.
There is a lot of information on its English website http://tronweb.super-nova.co.jp/homepage.html but it barely scratches the surface.
Yes, TRON was used for NTT DoCoMo i-mode phones and some Roland synthesisers, and most camera operating systems are also TRON forks. Yes, it runs on pretty much any 8, 16 or 32 bit architecture you can think of. Yes, it was used in home automation and cars, too.
But this system is also the basis for Mentor Graphics Nucleus RTOS, and eCos and RTEMS APIs, and that makes it BIG.