American drivers are now even more distracted by their phones. Pedestrian deaths are soaring.

Until relatively recently, good data on the problem of distracted driving has been hard to find. The government estimates that 3,522 people died because of it in 2021, but experts say the official number probably majorly undercounts the number of deaths, in part because police are rarely able to definitively prove that a driver was distracted right before a crash.

In the last few years, though, the data on distracted driving has gotten better. Cambridge Mobile Telematics is a company that partners with major insurance companies to offer downloadable apps that drivers can use...