housed inside the empty space of a standard two slice toaster

This little NetBSD toaster is just a normal toaster with a hardware mod, but the fact that it legitimately uses NetBSD to interface is quite impressive for this hack.

https://hardware.slashdot.org/story/05/08/11/1754253/the-netbsd-toaster

https://www.embeddedarm.com/blog/netbsd-toaster-powered-by-the-ts-7200-arm9-sbc/