I finally settled on a Bluetooth transmitter/receiver, the Avantree Saturn, which could be hooked up via a typical earphone socket to almost anything. I’m not sure that the signal quality is anything to shout about, but it worked fine.
http://www.youtube.com/watch?v=Ow2gDGoLcNc
Transmits to Bluetooth speakers just fine. Took a little while to figure out the ins and outs of connecting such devices. But the device works well, if you’re patient enough to figure out some of the blue flashing light sequences… Still not sure how I can configure an android or ios device or PC to RECEIVE hifi music via this dongle. But that’s not the dongle’s fault.
The range is limited of course, so at some point, I might look into a wifi transmitter for my hifi!