I really wish there was such an application. Something that worked really well, and allowed you to connect a camera (for instance a 20D/30D/40D/othe dSLR) to the iPod Touch/iPhone via the dock connector, and download (lower resolution versions) the photos directly from the camera. Even better would be a memory card -> iPod Touch/iPhone adapter. I'd like to be able to import the photos into the Photo application.
Anyway, unfortunatly as you probably know the App store agreement (or similar) states that you can't access non apple stuff or perhaps not anything external to the iPod/iPhone. Seeing as apple does not make an camera adapter for the iPod Touch/iPhone nothing "legit" will be coming anytime soon, unless from apple.