Not a purchase, but a gift. My Mom got me a cell phone holder that clamps on the handlebar. I tried using Google maps while riding on a business trip away from home, but (a) the battery drained down very quickly; and (b) the display was too small and dim to be useful. Looking at a map and writing down some basic directions in case memory fails is still better. I normally carry my cell in a baggie in my jersey pocket, after one ride I went back to the old way. Sorry, Mom, thanks for the thoughtful gift, but that was a waste of money.
(There's nothing wrong with getting lost, anyway.)