Yeah, I used to ride with a little speaker on one side of my helmet on the inside... nothing infuriated quite like a leisurely fun ride with the audio constantly telling me to make a u-turn or whatever because it found a route that was 57 minutes instead of 59.

I'd love a "I saw your suggestions, I selected one of them, don't give me any more suggestions" feature. This was on google maps.

As for detecting rain, that'd be a whole other algorithm.