Pithflow vs Aiko
Aiko and Pithflow both turn recordings into text on the device itself, so the audio never leaves your iPhone or iPad. Aiko is a $24 one-time transcriber for 100 languages. Pithflow writes the transcript while you record, tells the speakers apart and turns it into notes; it also dictates on Windows and Mac.
Short answer: both transcribe on your iPhone or iPad and never upload the audio. Aiko is a $24 one-time transcriber for 100 languages that works after the recording and has no speaker detection yet. Pithflow writes the transcript while you record, separates the speakers and writes the notes; the first 2 minutes of every recording are free.