So little to no button layout?
Here's your chitty concept art:
http://gabriel77cortez.deviantart.com/art/Chitty-Concept-Full-286657995
http://gabriel77cortez.deviantart.com/art/Chitty-Concept-Screen-286658164
http://gabriel77cortez.deviantart.com/art/Chitty-Concept-Back-and-Side-286658300
Anything close to what you asked for?
[edit]
* And yes I tried to draw in something GPS looking hing but decided it was too much work for something I wasn't even serious about so I ersased it, can still see that ugly "SPEED" writing there though...
* I did take it with a camera phone as I have no scanner nor tablet.
* The button layout is: Home>Menu>Power>Back>Search.
* Upper right corner has three lights in a vertical order. First one is green, which means the phone works fine, the second one is yellow, it's for when the device is experiencing problems with the software/hardware or when a search on internet is complicated. Red is the rarest one, it's when something has gone really wrong inside of it, be it the software or hardware or a virus or whatever, something is broken in it and the red light flashes to let you know.
* It's strapped on with 3 straps, so that in case you do fall down or something and one strap comes loose you still have two straps keeping it on your arm.
* It's a cold metallic design as I find it most fitting for a pip-boy esque device.