As someone who spends his time writing in High Level languages (though I have done lower level stuff in the distant past) these kinds of embedded computers hold a real fascination for me.
On my long term list of things to-do is get back into electronics and learn Ada (mostly because it's a million miles away from PHP).
Learning Ada is worth your while, embedded or no. Hint: If you have a problem and you find yourself reaching for C++, consider Ada instead. It's probably powerful enough for the task, safer, and more readable (therefore maintainable).
Try implementing Unix utilities (cat, ls, echo) in it for a weekend of fun. :)
On my long term list of things to-do is get back into electronics and learn Ada (mostly because it's a million miles away from PHP).