I had the idea for quite some time but never got around to develop it. In November of 2021 we had a Hackathon at my company and I used that opportunity to implement a proof of concept.
Afterwards I completely rewrote the App and tested it personally. While Speechy worked nice itself the transcriptions on iOS 15 weren't as nice so I stopped using it personally.
With iOS 16 the transcription results did improve so I started developing again.
With iOS 17 the transcription results did improve drastically up to the point that it is really a time saver for all voice messages.