I imagine some
(or many
) of you have already seen this, but I just came across it today; this guy is attempting to "resurrect" a Psion Series 5 by modernizing it within the existing body. He started in late 2015 and has been working on it very part-time. Much of it is way beyond my end-user understanding, but it's interesting seeing the level of detail and the complexities involved. There have been occasional posts here about doing the same thing with a Jornada or MobilePro, and I always figured it would be pretty difficult to pull off.
https://hackaday.io/project/4042-psio
It'd be cool if he actually succeeds!