I spent a couple of hours on a bike ride earlier this month with Rex Hammock. Rather than have him pay for a CitiBike, I rode my Giant, and used my key to check out a bike for him.

We went uptown, then downtown, when the 45 minutes were up we checked in the original bike and he got a new one. 25 minutes later we're ready to finish the ride. Since Rex was staying at a hotel downtown, and I live uptown, we split -- each going our own way.

When I was about a mile north, I realized this wasn't going to work. Rex needed my key to check the bike in. So I pulled over and dialed him on his cell phone.

No answer. So I left a message, and kept going north. Until I heard my phone ring. Of course I pulled over. It was Rex. He saw my name flash on his Pebble watch, and realized it must have been something important. We met up, returned the bike, he checked one out on his own, and it had a happy ending.