I don't recommend anything I haven't tried. But I will tell you what I'd do. Do a search for Van and see what they are using. I went with the monitor I have (xenarc 700TSV) because everyone that had done 350Z's said it was a perfect fit. So try to find people that have already done what you want to do. When you get into touchsceens, the price goes up really fast with size. Heck, I just found a $100 device that almost wipes out the need for a touchscreen altogether.....
http://www.soundgraph.com/Eng_/Produ...=1&leftMenu=26
It's got 5 programmable buttons, which cover the main screens like: Navigation, Music, Satellite Radio, pictures, and I programmed the 5th button just to go to the home screen. It's got fast forward, rewind, play/pause, previous song (works with music and radio), next song, volume, mute, and a scroll knob to go through music or stations. It's not perfect, but for a budget, would work fine while mobile. However, mounting it is a bear as it's made for a desktop and not a radio hole. Another problem with it, in your plan, is that it has to be tied into the motherboard power. Not sure how you could do it with a laptop. But even then, could it be more cost effective to get a carputer, larger non-touchmonitor, and an Imon? Or go with the laptop and and a smaller touch.
Come to think of it, since I have installed the Imon, I don't remember ever using the touchscreen while driving.