I went with GROM on my Mazda6 last year. I bought off eBay and the module that at the time was suitable to my car was $86. I installed it myself. They sell an adapter that is probably appropriate to your Camry's head unit.
http://gromaudio.com/store/all-toy.html
Most of them act like CD changers. They can typically play the first several playlists on the device or alternatively they have a mode where you can play whatever is cued up on the device. If you have steering wheel controls, you can use them to change tracks, etc, on the current playlist/album. I mostly only use it if I drive long-distance, but it's nice to have.
It looks like the latest ones offer a number of features mine from last year didn't have.
(Also I see you want to put the iPod touch in, which ought to be fine, but do be warned that my original idea, of getting a disk-based iPod and leaving it in the car, isn't a good idea in the North in the winter, as the iPod will seize up and not work until you bring it inside and warm it up.
).