A genius idea, bur all is lost in the execution. As others have pointed out map is useless, but push up button and you get turn by turn directions which would be perfect, however the real issue is that for some reason the gps localization is terrible. It seems to have hardly any idea whatsoever where you actually are. I have numerous gps apps on the iPhone and the accuracy in all but this one is excellent. Currently nearly unusable.
binarybum about MapsGPS for Pebble - Smartwatch maps and directions