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Here is some Applescript code to go with grgarside's Answer 

I tested and it works. The code needs to be saved as a stay open Application.

When the app is running it will try press the right arrow right. In this code I have set it to ten seconds return 10 But depending on the length of time you set this could be a little bit of a pain if you switch out of aperture for some reason or want to quit the app.

So I have included a  CAPS  lock key down detection. Which will quit the App on the next iteration. You don't have to use it but it is there if you need to.

  on idle
    if isShiftKeyPressed() then
        -- IF CAPS LOCK IS DOWN THE APP WILL QUIT
        display notification with title "Arrow Right App" subtitle "quiting right Arrow App"
        quit me
    end if
    try
        tell application "System Events"
            tell application process "Aparture"
                key code 124
            end tell
        end tell
    end try
    return 10
end idle

on isShiftKeyPressed()

    return (do shell script "/usr/bin/python -c 'import Cocoa; print Cocoa.NSEvent.modifierFlags() &amp; Cocoa. NSAlphaShiftKeyMask &gt; 1'") is "True"
end isShiftKeyPressed


I have tested this in Aperture and it worked as grgarside suggested.

Remember to change the line tell application process "Aparture" to you application if it is not Aperture.