I'm presently hard at work supporting turn-by-turn spoken directions in Bike Tracker. I've requested access to the "Ride with GPS" API to give users direct access to their routes on "Ride with GPS", but even if I'm denied, the app will still be able to load TCX files, which you can export from the Ride with GPS web page.
There are other apps that support turn-by-turn, but after using many of them, I've always come away less-than-impressed. The problem usually comes down to the timing and frequency of turn reminders. I've put a lot of work into ensuring that Bike Tracker's turn reminders will be timely and accurate, and there will be no overkill.
Another thing that simply isn't handled well in other apps is going "off course". Many just tell you that you've gone off course and they expect you to LOOK AT the map to figure out what you've done wrong. Bike Tracker will provide spoken information about track errors (like taking a wrong turn) and guide you back on course without you having to look at your screen as you ride, or to pull over to check.
The turn-by-turn feature is still being thoroughly tested, but it should be available before the end of June.