If smartphones are able to detect whether a driver is looking directly at the device, criminally selfish drivers may simply hold the device in front of them while upright. We will have traded one problem for another.
Allowing users to look away from the roadway for 12 seconds is an invitation to a slaughter. 25mph is a typical speed through a residential neighborhood. At that speed, a vehicle will travel 440 feet in 12 seconds.
There is no technical solution that will allow passengers to text and play games while restricting the driver from doing so. We should take our cue from liquor laws. We don't allow open containers of alcohol in moving motor vehicles, even though it infringes upon a passenger's right to drink. We should require smartphone manufacturers to add a capability to prevent texting or game playing by drivers or passengers while the engine is running, perhaps via the detection of ignition noise.
And we should change the laws by making the punishment for texting while driving the same as for DUI.