Related impractical fun: you could fit a small Lisp (such as standard R7RS Scheme) in some PC motherboard flash chips used for the BIOS/bootstrap, using Coreboot. Maybe ThinkPad X200 or a Coreboot-friendly Chromebook.
What happened was that the DOS flash image got corrupted somehow, so Noko implemented missing bits in his lisp implementation and made the phone boot directly into it. Since all the software he used was written in his Lisp, there was not much of a difference in usability :-)