Many car accidents are caused by drivers using their phones while driving, with many deaths and permanent injuries.

Make phones lock when a speed of more than 5 miles (8 kilometers) an hour is detected.  Require the user to key in a code that the phone randomly generates.  If not entered within 5 or 10 seconds, that code should change and the clock should be restarted.

This will make it much more difficult for drivers to text while driving, while still allowing passengers to use their phones.  A driver will need to both look at the screen AND enter keys within 5 or 10 seconds, something that is very difficult to do while driving, but is quite doable otherwise.

In addition, the phone could be relocked again after a minute or two of disuse.  And after a few missed attempts, the phone could lock for 15 minutes.  As always, calling emergency services would still be possible.

A manufacturer can provide a mechanism that allows the elderly or those with handicaps to have more time to enter the code.