This may be a slightly different answer than you are looking for (not app solutions persay) but there are a few stripped down nav products that in the process of development or have recently entered the market that you could look at. Using one of these (or just investing in a bicycle mount so you can use bluetooth headphones with google maps) may give you more flexibility/control to get updated directions as you ride. I have been conducting research on the subject for a project for my Masters and one of the new stripped down, turn-by-turn navs in development: is Beeline, which is able for pre-order now https://beeline.co/. Although I am not sure what the audio capabilities are for it.
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Conducting research on bicycle navigation systems for my MSc., make your voice heard on by taking the survey here: https://lse.eu.qualtrics.com/jfe/for...diKglMv9QWhBbL