This company makes products which may serve your friends needs:-
http://www.marmitek.com/en/products/audio-video-at-home/listen-anywhere.php
I think that your friend is looking at spending upwards of £500 (and more likely somewhere near £1,000) - for that kind of money I’d want to hear and see what such a system could do (when connected to my hi-fi).
You might find another company that is making a more flexible system, consisting of an RF sender unit together with multiple receivers that can be connected to active speakers of your choice (or an amp plus speakers).
I don’t think anyone will supply a system controlled by motion detectors.