Wireless audio from soundcard?

I work in a large retail store, and we've recently decided to implement a custom customer queuing system with a large screen displaying the current customers number and a loudspeaker announcement to acompany it.

I need to find a way to get the loudspeaker announcement that goes with it to play at the opposite end of the store, without running any cable from the source pc to the new set of speakers. Ideally it will just be a set of speakers plugged into a reciever of some kind, but if neccessary I can maybe scrape together a small basic box to run them if i need a more sophisticated software solution.

Any ideas?