Way to stream photos of a folder as slideshow to Apple TV?

Basically, I would like to choose a folder full of photos, and have the content streamed to my Apple TV as a slideshow.

Now here is the kicker: I want to add photos to the folder WHILE the slideshow is streaming, so the slideshow will get longer as the night goes on.

One idea is to use a dropbox folder, and use my iPhone to take new photos and upload to dropbox automatically, and have them instantly added to the slideshow.

Any ideas?

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EDIT: I could use AirParrot to mirror my Mac's display on Apple TV. Now all I would need is the slideshow app that can automatically add the new photos in a folder to the slideshow.