Currently most of the audio equipment in my home is connected via Airplay; while definitely Apple-centric, there is enough third party support from the likes of Bose and Pioneer that I am quite happy with the setup.
I do have a few bluetooth speakers, too, like the Jawbone Jambox and the Logitech UE Mobile Boombox. I primarily use these in the garage, on the deck, or in the basement and pair them up with my iPhone. This works well enough until I want a track to play throughout the whole house; while Airplay can easily handle multiple speakers, streaming to Bluetooth speakers is largely a one-to-one affair.
I've been trying to find a way to bridge Airplay to Bluetooth, but since Airplay is fairly well controlled by Apple, there doesn't seem to be a simple box that can enable this.
The only solution I've found so far is to use an Android device to bridge the two. There are a number of unofficial Airplay apps available in Google Play; I am using AirBubble (free to try, $1.99 to buy) It works as advertised; I launched it on my Nexus 7 and it immediately showed up as an Airplay destination on my iOS and Mac devices.
I then paired the UE Mobile Boombox to my Nexus 7, and started playing a track on my Mac. Within a few seconds, Airplay connected to my Nexus 7 and then immediately came out of the bluetooth speakers.
This is a fairly clunky setup (how many OSes does it take a geek to play one song after all ) but works amazingly well. It lets me bring the bluetooth speaker anywhere within range of the Nexus 7 and add it as an multi-speaker output to a song playing in iOS or Mac.
I am trying to find a way to accomplish the same thing with a Raspberry Pi rather than an Android device; there are Airplay receiver scripts available but I haven't seen anyone out there try this sort of configuration with the Pi yet. Might have to give it a shot.