As a daily bike commuter around Boston, this idea terrifies me. Multitasking is extremely dangerous while biking. There are already enough bikers out there who choose to distract themselves with earphones and music while biking. Reading a text message while weaving in traffic is a recipe for disaster. When you're on a bike, be on the bike.
I am a daily bike commuter in Anchorage where we have tons of dedicated trails. I can ride all the way to work 7 miles and I only have to cross a couple streets.
This would be fine. better than pulling my phone out of my pocket while riding (which is what I do now)