I recently picked up a "bento box" bag I think they're called? Attaches around the stem spacers and top tube. The top panel of the bag is clear on top for a smart phone, which I've been putting my phone in and using Strava with it. But then last night when riding in 34° weather with Strava running for 1.5 hours, my iPhone battery didn't really take too well to that. I think the cold and continuous app running made it think the battery was konked out. Luckily a guy on the ride with us had a little emergency iPhone charger battery pack that he let me use, which gave it a little boost. On the way back I kept the phone stashed in my windbreaker pocket.