This is a great idea. A virtual audio device that sits in the path of any audio stream and provides live transcription, that would be huge for video conferencing, lectures, podcasts.

MetalRT's STT numbers make this feasible: 70 seconds of audio transcribed in 101ms means you could process audio chunks in real-time with massive headroom. The latency would be imperceptible.

We haven't built this yet but it's a compelling use case. CoreAudio supports virtual audio devices (aggregate devices) that could pipe audio through the pipeline. If anyone in this thread has experience building macOS audio HAL plugins and wants to collaborate, we're very open to contributions, RCLI is MIT.