I'm trying to figure out whether to switch to a Garmin 510 or use apps on my iPhone 5. I have used my iPhone 4 and I recently upgraded to iphone 5. I like using the apps and I have used cyclemeter, mapmyride & Strava. How does the accuracy of these apps compare to Garmin 510 especially with elevation? I know a lot of people are concerned with the battery on smartphones and that is certainly an issue with me. Also, is it crazy to have your iPhone on you and purchase a Garmin 510? That's what I would to do to make sure I had a way to get in touch with someone in case of emergencies. I would appreciate peoples thoughts on this. Thanks!