Doesn't the Ridewith GPS phone app do all of this?

As was said above, the phone will burn through battery charge very quickly. Last year's Bike Virginia went all gps last year and those without Wahoo/Garmin had to use their phones. Some (my brother included) waited until ride day to figure that out. There is a setting...somewhere...to turn off the screen except when a turn or cue is needed, but lots of folks had a hard time figuring it all out.

Here is how I attempted to solve the problem: I later that year upgraded my Wahoo and gave my old one to Luddite Brother. So far, it has not left his mantle, but it's only been a year.