I occasionally flirt with this idea,too. If I had the time... I would start with Chumby for the hardware design. I believe it is open source, though you have to agree to contribute back any changes/improvements to the Chumby folks. For the software, I would use Android. And for any misc. circuit stuff, I would experiment using Arduino. (I learned to solder my first circuit for an Arduino project of my mine last year.) The one book on my bookshelf that I reference very often is "Practical Electronics for Inventors" by Paul Scherz