Some people already do what you are looking for. I was researching digital photo storage and on a photo forum there were several photographers who liked using certain Windows-based handhelds because they could get both a large drive for storage and a decent color screen for image reviewing. There are a few photographer-oriented utilities written for these Windows handhelds to do things like check those RAW files up close to see which ones are in focus. Nothing quite like that on the Mac side yet.