Wireless Hearing aids are something new. Its a new technology for hearing comprimise people. FM listening systems are now coming with wireless receivers integrated with the use of hearing aids.
A separate wireless microphone can be given to other person to in a restaurant, in the car, during leisure time, in the shopping mall, at lectures, in noisy area. So the voice can be transmitted wirelessly to the hearing aids from the mic eliminating the effects of distance and background noise.