On the Make: magazine blog, they recently posted a piece about the evolution of a project. It was an iPod remote from last year that has gone from a "start and stop" only device to a full featured remote. It is a lovely piece of tech, powered by Arduino hardware. Arduinos are open-source circuit boards and software you can use to develop interfaces with all sorts of electronics.
I remember reading the first post about this remote last fall and being interested in where he would take this project, mostly because I love seeing what people do with Altoids tins. I have to admit hooking one up to a giant "Easy" button for my car never really occurred to me, though.
I really like the idea of building my own remote; partly so I can say I did it, but also because it would be a nicer way to get my iPod or iPhone (depending) working nicely with my car stereo.
Honestly I only understand about half of what he's talking about in this article, but I'm good at following instructions and I am reasonably handy with a soldering iron, so this doesn't look completely unreasonable. If I do end up building one I'll be sure to post all about it for you. In the meantime, have you built an unholy alliance between your Roomba and your iMac, or any other variety of Mac Tech Mashup? Tell me about it, I'd love to see what you all can do!