Enzyme, one of the most active member of our forum, has published on his blog a tutorial showing how you can use Action(s) with DropBox and your iPhone. Its shows how you can very easily apply effects on pictures taken from your iPhone.
Have a look, it will for sure give you some ideas!

iPhone and DropBox hack: WATCH and EXECUTE
http://enzyme-play.blogspot.com/2011/02/iphone-and-dropbox-hack-watch-and.html