Gateway provides a text messaging prohibitor phone App for teen & youth drivers and employee drivers driving fleet vehicles that prevent an accident due to distracted drivers when a vehicle is moving?  Distractive Driving

This Prohibitor App works with cell phones, hand held computers and laptops that operate in a vehicle. The blocking app removes the temptation of your employee and family member drivers from texting or browsing when a vehicle is moving which then reduces the chance of an accident from distracted driving of cell/smart phone or mobile devices. This text blocking app is the first to enforce distracted driving prevention.

And it's very easy to implement and use.

The text blocking app is a solution that communicates directly to the vehicle's OBD and knows exactly when it is moving. It is not GPS based or based on tower triangulation, so the strength of your service does not matter. The car tells the phone what it needs to know.

If the vehicle is determined to be moving then the phone app determines which communication methods are or are not allowed. These policies or rules are managed by a user via a web site.  Emergency and ICE numbers are always allowed.