There's a whole market of suppliers that's been going strong for decades. Especially for safety-critical embedded with untrusted, Linux/POSIX apps in separate partitions. QNX is one of best examples far as commercial adoption:

http://www.qnx.com/content/qnx/en/products/neutrino-rtos/neu...

Example of embedded product in case you wonder about performance cost of all that isolation, healing, and context switching:

https://youtu.be/vPo6gl8N0wM?t=1m20s

EDIT to add the QNX Desktop Demo that came on a single floppy. Throwing it in since you were mentioning resource-constrained systems further down. A floppy is 1.44MB with base QNX running in ROM's of embedded systems. Can scale such architectures it up or down however you wish. :)

http://crackberry.com/heres-how-qnx-looked-1999-running-144m...