Shuttle Book size core-duo 500GB 3.5inch HDD PC.
 

http://www.theinquirer.net/?article=32312

This is not as flash as they might think. There has been book PC's, and Car PC's, around this size or less, for ages. It would be worth looking at links in the Digital cinema camera projects for small Car PC's. Having said that, this is another option for the DIY camera maker, or any normal camera format.