Is it possible to AirPlay music from a Mac to an iPhone?

I want to be able to play music to various 'real' AirPlay speakers, like my Apple TV and AirPort Express, but I'd also like to be able to put my headphones on to my iPhone when I need to go to a part of the house without speakers nearby and continue the tunes in the same place they're playing throughout the rest of the house.

Is there any app that acts as an AirPlay receiver, and will let me do this? I know there are a few for video, but I just want audio.

I am aware of Airfoil, but I'd rather not change the output mechanism from AirPlay to Airfoil - I'd like to stick with Airplay for consistency and less hassle, to be honest. I'm sure there must be just a simple iOS app that enables an AirPlay receiver on the device...