With photocontrol you can control a picture presentation with your iPhone. You may also want to look at the source for the server application.
With photocontrol you can control a presentation of photos with your iPhone or with your iPod touch. All you need to do is to install the photocontrol software via the App-Store on your iPhone or your iPod touch. Furthermore you need to install an server application on your Macintosh which delivers the photos on your Macintosh to your iPhone.
The iPhone Application can be found in the App-Store here. The server application for the Macintosh can be found in the downloads section of the photocontrol website.
The code is licensed under the gpl v3.