Gus has written up a way to make a Raspberry Pi act as an AirPlay receiver. He uses a piece of open source software called Shairport Sync to do it. As he comments, it’s a quick-and-cheap way of getting some speakers wirelessly available to your Apple device as a playback facility. Take a look at the write-up here.
Pimoroni have already done all the hard work – they created an awesome one line installer for Shairplay-sync that works flawlessly!
https://learn.pimoroni.com/tutorial/sandyj/streaming-airplay-to-your-pi