re: In other tech news, how long before a detector comes out for this?

I'm guessing something like this would be used to supplement evidence in observable offenses, not to give cops a reason to pull over every car that triggers the detector. However, if the detector goes off and a cop can see the driver using her phone, probably makes for a stronger case, especially in those states that have specific laws against texting vs. universal laws against operating a phone while driving. Not sure how easy it is to prove on the spot that someone who was observed holding a phone in the car was violating a specific anti-texting law.