Ya this is just another cash grab. 
I wonder how they will approach testing drivers for being high? If approved devices are accurate enough to figure out if you smoked in the morning and it's night time, you're obviously fine, but will it know that, or will you face a dui. 
With alchohol you can measure an exact limit. 
First guy to invent the pocket device for individuals to measure if you're too high to drive, take the money.