I am using an iPhone as both my phone and via an app (I use cyclemeter but there are others) tracking many aspects of my cycling activities. The app is configured to automatically email me the stats following my ride (as well as on-phone and cloud storage) . I also have a bicycle computer on my two most used bicycles... as a backup to the data.

The old, cheap, little, low tech, bicycle computers give me the at-a-glance dashboard info I've become accustomed to. And the app runs quietly in it's Ziploc bag (with an ID and some cash) in my jersey pocket. So far.... battery life hasn't been a problem.... but this is my first season so I haven't fully tested that part. But I think since I am not using the screen... battery life should be fine.

I am also using my phone with apps (and hardware) to control my TV, Cable, security cameras, and home automation [lighting].