I'll ride with the phone, and turned on. No, I can't imagine trying to use it though while riding. I typically will stop on the side of the road somewhere convenient if I need to respond to a text or whatnot. Also use the phone to run the RoadID app, which gives the family a link to find out where I am (and this in turn cuts down on the texts, so a win-win).
Finally, once in a while the phone is nice to have if coming across anything scenic I might want a photo of.