A lot of the mini-PCs based on netbook technology (like Ion-2) are designed to be fastened directly to the back of any VESA compliant monitor.
The combination makes for a really slick all-in-one machine. It is a bit tricky to find LCD monitors built with touchscreen included but they do exist.
However, adding a battery backup that could run a thing like that for more than 20 minutes would be quite heavy and painful to haul around.