Playback on an iOS device can be accomplished in the Apple ecosystem using a piece of software called Airfoil on a Mac and an app called Airfoil Satellite on the iOS device. Both are sold by Rogue Amoeba, a long-time Mac developer. They produce a number of useful audio utilities for the Mac. It is definitely an inelegant workaround, and it certainly does not provide the highest quality audio experience, but with a solid wifi network in my house, it usually does the job for me when I don’t have access to my usual listening setup. (darn kids!)