It was developed for educating people about AIDS in Africa, where radios are popular but batteries are expensive.

Invented by Trevor Baylis, he orignally set up production in Africa after many knockbacks:
http://www.cityspeakersinternational.co.uk/TrevorBaylisOBE.htm

Bayliss Brands, his inventor's help company:
http://tbf.websfor.org/tbb/home/home.asp

Gareth