A ringing phone in the car may be quite dangerous as the driver unintentionally takes his/her eyes off the road. However the latest offering from Sprint may help solve this problem. Their Drive First App limits the smartphone's functionality when it senses that the driver is behind the wheel.
The app does this by using the GPS radio on the handset. It detects when the vehicle is in motion and locks the device once the speed exceeds 10 miles per hour. When it is in this mode, all incoming calls are automatically forwarded to voice-mail and email and SMS alerts are silenced. An alert will also be sent if required to let them know that you are driving.
This service will cost $2 a month, with a 15 day free trial which allows you to test out the features before you commit to the purchase. While I am sure it won't attract many customers it may be useful for Young and inexperienced drivers who's parents will feel much safer knowing their children are not on their phones while driving.
source - Sprint