poor range, low battery life, disconnects for no good reason, won't connect sometimes, etc.). is incredibly intrusive, and its Bluetooth has all the problems of every other Bluetooth device I've ever paired with my iPhone, iPad, and Mac (i.e. The problem w/ most hearing aids is they require a 'streamer', which is a mic + Bluetooth device that you wear like a necklace (it MUST hang around your neck).
I've tried a lot (maybe all?) of the iPhone-based hearing aid apps, and the problem is the iPhone mic: it just wasn't made to act as a hearing aid mic, it has completely different requirements.