I haven't found the need to see my iPhone when riding. The screen switches off after a few minutes anyway.

You can set it to never turn off the screen, but then you start running into battery limitations. I've found that when running Cyclemeter, which is constantly using the GPS, with the screen off and the phone in a pocket, the battery is half drained after a few hours.

I'd hate to need to call for help and have a dead battery.