The NHTSA seems to have shot down Tesla's request to allow manual control of the vehicle via a touchscreen in their latest rule making regarding automated driving systems. I'd be curious to see how well such a system would work... I'm skeptical!
NHTSA does not agree with Tesla that it is necessary at this time that the definition for manually operated driving controls account for the use of tablets or cell phones to control the vehicle. The new definition is meant to encompass traditional driving controls, not future controls that have not yet been developed.