For the hard of hearing like me the killer application would be live transcription in a noisy setting like a meetup or party, with source separation and grouping of speech from different speakers. Could be life-changing.

(Android's Live Transcribe is very good now but doesn't even try to separate which words are from different speakers.)

* Automatic speech recognition (ASR) systems have progressed to the point where humans can interact with computing devices using speech. However, the distance between a device and the speaker will cause a loss in speech quality and therefore impact the effectiveness of ASR performance. As such, there is a greater need to have reliable voice capture for far-field speech recognition. The launch of Amazon Echo devices prompted the use of far-field ASR in the consumer electronics space, as it allows its users to interact with the device from several meters away by using microphone array processing techniques.*

https://assets.amazon.science/da/c2/71f5f9fa49f585a4616e49d5...