When I changed shoes recently, and moved the Nike + sensor from one of my old shoes to the new ones, it didn’t connect. And, of course, I didn’t check before I walked out the door for a run. I spent a couple minutes trying to get it to connect before I just took off without having any tracking.
When I got back, I pulled out the insert, and the sensor, and then clicked the button on the sensor. It’s on the bottom, away from the Nike + logo. When I then tried to start a run, the iPod picked it up right away.
Little trick that made me wish I’d taken 2 minutes outside before the run to try it.