Dropbox released the upload function on its beta version of the Dropbox app. Users have only been able to store files on the app thus far. Now, they can continue to use the service as they would on a computer. So far, only Andriod devices have the enabled functionality.
http://www.engadget.com/2012/02/24/dropbox-app-drops-the-beta-automatic-photo-upload-goes-official/