Originally Posted by rm -rf

Try Osmand You can download some state maps for free, and a one-time subscription for more maps is cheap (I think it's $6)

I was on a ride with another rider that was getting turn-by-turn voice prompts. I thought it was giving too many advance notices of upcoming turns, but perhaps that's configurable. See some screen shots in this post. I've not used it for bike navigation, other than uploading a route file and seeing that it shows on the maps correctly. (It was kind of confusing where to put the routes so that osmand could find them.)