I was going to buy a garmin for my bike, I found an android app called my tracks and decided to try it on my smart phone. I have used it twice on the bike and a couple of times while in the car. So far it has been acurate and is nice since you can upload the information directly to google maps. The information provided is max percent of climbs, max percent of decents, max speed, average speed both moving and overall. maps your route on google maps, links directly to my timex heart rate monitor, and displays charts showing the profile of your ride and charts your speed relative to ride contour.
So far with this app I can not see the reason to purchase the Garmin with this app avaliable for free.
Would like to see if any others have used their smart phones.