I have my I phone on the bars, using cyclemeter, and the Wahoo sensors.

On one ride I heard a thump, like a rock flew up and hit something. It did, the spoke magnet. Cyclemeter lost the signel and hung up. Corrupted the database for that ride. I emailed the file to Cyclemeter, and they examined it and told me how to troubleshoot the sensors. Awesome support.

Battery life. I have an external battery in a water bottle, USB cable up to phone.