The device will even be able to distinguish between the radio waves used by texts and the waves used by calls, which are of a different frequency, ComSonics manager Malcom McIntyre told the Virginian-Pilot. That ability would be useful in Virginia and many other states, where it's legal for adults to talk on a cellphone while driving, but not to text. (Which seems silly. Research has found that having phone conversations while driving is dangerous, too.) It's unclear, however, how the device will be able to distinguish between texting on the part of the driver, versus passengers in the same car.