Hackable? Perhaps. i had the same thought you did a few months back when i found a photo key chain for $10. unfortunately when i cracked it open, it was anything BUT hackable. Or, I suppose, for my purposes. The main electronics were just a big blob of potting epoxy, the LCD was tightly soldered to the tiny PCB, and gosh, even the USB connector was proprietary. Ultimately, I found, that if you have to use special software to transfer photos, there's a good chance the software won't be an attack vector either.
My ultimate issue was there simply weren't' any parts that had already had work performed with them. I had nobody elses shoulders to ride on, and well, my time isn't so free that I could take the time to reverse-engineer the thing.
NOW, don't let my experience darken your mood with the project. Those things are cheap. Dirt cheap. Pick one up, perhaps you will have a very different result from wht I did.
Either way, good luck!