Mobile computing is one of those sticky subjects. Modern mobile computing runs around as cell phones and PDAs. Then there's the crazy people working on a "wearable comping" system that keeps them partially in a computer generated world at all times.
I'm not THAT crazy. I look more for something resembling military computing. There when you need it, mostly hidden when not. One thing that popped up recently is a tech outline of a wearable PC. See link here:
Now, I've run across enough hardware to consider how to build one. A base board system would distribute controls as needed. The main CPU would be a Gumstix, with video breakout and some extra IO. I'm hoping they have a lot of breakout of the video and input hardware. This could be hooked into a 2.2" touchscreen TFT screen ($50 from Mouser). The base board also has built in audio connectors. A 400MHz Gumstix running Linux may be powerful enough to run a voice recognition software package, providing hands free access. A subsystem microcontroller would control stuff like LEDs, IO, touchscreen, etc. I'd probably integrate a pseudo-IMU so that motion may be used to do some control, such as a mouse. I might also wire in a glove or something to allow controlled clicking, or move the IMU to the back of the hand there (now there's an idea...)
Depending on size, a LION battery set can be hidden either behind the board or elsewhere (depending on ergonomics and design). Now, final design is that the casing could be made to look rather professional with a vac-formed casing.