It depends on how much you want to know, and what level you want to get to. I would say that a linux based touch-screen device is actually pretty high level (it is running linux afterall).
If you want to make something like this you can buy things premade like the gumstix (http://www.gumstix.com/) that can get you there pretty quick. Then you can hack from there.
PCBs and lower level stuff is another animal. I mean there is just a huge amount of completely different concepts involved. Designing a PCB for some 8 bit microcontroller running at 32KHz is nothing like designing a radio board with an antenna.
If you want to make something like this you can buy things premade like the gumstix (http://www.gumstix.com/) that can get you there pretty quick. Then you can hack from there.
PCBs and lower level stuff is another animal. I mean there is just a huge amount of completely different concepts involved. Designing a PCB for some 8 bit microcontroller running at 32KHz is nothing like designing a radio board with an antenna.