Controlling a Nano with photoelectric sensors

[greatking]

I'm a composer working on an arts project. Specifically, a soundscape installation. I'd like to know
if there's a patch available or creatable to cause an iPod (nano or
shuffle) to recieve an electric impulse from a photoelectric sensor -
they put out current in the milliamps and there are devices that can convert that signal to yes,no messages. - that would send a play message
to a playlist on the nano. When the first song of the playlist is
finished, the iPod would autopause until the next impulse from the
photoelectric sensor. It wouldn't recognize any messages from the sensor until the song has finished playing. At the end of the playlist, the patch would tell
the iPod to cycle to the beginning of the playlist - essentially a
continuously playing playlist that paused at the end of each song. I
guess I could start everything by placing the iPod in play mode at the
outset but if there were a way to make the iPod default to the first
song in the playlist, that would be fabulous.

[gnu]

1. I'm 100% percent sure something like that doesn't exist, since not many people would need it
2. It wouldn't work anyway, since the shuffle isn't supported by rockbox and the nano has no mic/line in -> it couldn't read your signals.

[Llorean]

If someone solved the issue of communications as used for the accessories, then it could be doable by way of a custom connection to the dock port, but that's no easy task, and probably still requires reverse engineering work.

[saratoga]

Since no one can run code on a Shuffle, thats out.

I don't think theres a way to input a signal easily to a Nano without writing a lot of code, so thats probably out too.

You could use a 4/5G with the line in connector for signaling.  Thats currently supported, so the amount of hacking involved would be relatively mild.  You'd basically just need to write something that monitored the line in and responded to changes.  Otherwise, you're looking at doing a lot of extra programming to get the apple accessory interface working.