Early PDAs were glorified diaries cum address books, hence the PDA moniker (for Personal Digital Assistant). We've moved on since then, though, and in the modern world of iPods and camera phones, PDAs want to make your life fun. It's not enough that they get you to meetings on time, or enable you to call the right people if you're going to be late; they also have to keep you entertained while you're stuck in planes, trains and traffic jams.
These four PDAs all have built-in cameras. They won't replace your regular digital camera, because they lack all but the most basic camera features, but they're handy for quick snapshots. They can also function as MP3 players, although you'll need to add a largeish memory card and a pair of decent headphones to make the most of this feature. The real beauty of this approach, however, is that you only have to charge and carry one device for work and play.