Is there a workaround to enable streaming music to multiple speakers from iOS? It is well documented that you cannot stream to more than one AirPlay compatible device through iOS. (In an early developer build of 4.0 the functionality was put in but was taken out in the GM). 

I am aware you can stream iTunes content to multiple devices and even use the Apple Remote App to control multiple devices.

However, I am looking for a solution that allows me to play a Pandora/Spotify/Slacker/Songza app on my iOS device and allow me to stream that music to multiple devices.

The only solution I have found right now is a complex solution using Rogue Ameoba's AirPlay Speakers app on the iMac but there is about a 4 second lag and additionally, once you have captured audio, you have to manually go to the computer to cancel the connection to allow for other connections.

Does anyone have other workarounds or solutions to this challenge?
So far I haven't found a good all-digital solution.  I typically use an audio splitter at the computer, and a whole house FM transmitter plus speakers so I hear the sound locally and through FM radios I place wherever I want the sound.

Since everything is transmitted real time, there's no sync delay as you move from room to room, and the transmitter I have is strong enough to receive using a boombox out in the yard while I'm working outside, without risking any expensive equipment in case it gets kicked around the yard or rained on a little bit.

I use a modified Belkin Tunecast transmitter.  I disassembled it, and added a length of wire to the antenna connection to stretch the distance it transmits a little.  There are some legal ramifications to this depending on the country you live in.  If you want a more professional solution, there are a few places that sell whole-house FM transmitters fairly inexpensively.

You could also connect the transmitter to the airplay receiver, entertainment center, iPad, Android phone, windows PCs, or any other audio device, and the receivers are cheap - you can get an FM radio from the dollar store for a dollar, and amplified speakers for a dollar, so expanding the system is cheap.  It's very flexible.

The biggest drawback is quality.  It's not bad, but you can't expect even CD quality from it, nevermind high quality audio.  It's ok for music and voice, but audiophiles will be offended.  Airplay is CD quality, and the difference would be noticeable.