Triggering music by proximity

I'm trying to get a small model to play a piece of music when someone comes close.
Been thinking along the lines of:

Proximity sensor (IR rangefinder?) -> arduino nano -> ripped up iPod -> speaker

But I have a nasty feeling I'd need an amp in there to ramp up the iPod output.
I saw the adafruit sound shield ( http://oomlout.co.uk/collections/arduino/products/arduino-wave-shield-adafruit ) , would that need an amp to run a small speaker?
The size of a full arduino wouldn't be ideal but if it'd save some complexity (I'd be a bit shaky
on too much integration circuitry) it might be worth it.

I'd also like some alternatives for the IR rangefinder as short of drilling holes in the model I'm not convinced
It'd work reliably? Maybe just a light dependant resistor?

I saw the adafruit sound shield ( http://oomlout.co.uk/collections/arduino/products/arduino-wave-shield-adafruit ) , would that need an amp to run a small speaker?

Yes if you look at the pictures it contains a small amplifier that you can use to drive a speaker.

I'd also like some alternatives for the IR rangefinder

They are the best you will get.

Maybe just a light dependant resistor?

You wont get any distance measurement and you will still need a hole to let the light in.

Seems to me a small Android smartphone would do all of this. Movement detection via the camera- I'm sure there are plenty of apps.