I set Shep to ignore b/c of previous comments, but I have seen his earlier questions and they're fair enough.
I do filter past slow-moving traffic on my commute quite regularly, and when I see that a driver is likely to be on their phone, usually because of the enormous gap between them and the driver in front, I will pass them slowly and the helmet camera records what it records - the registration of the vehicle and the phone use.
I can usually easily see from the footage whether they had any hands on the wheel, both on the phone, typing away on it, illuminated screen, power cable attached etc.
When I have time within the next 7 days I simply upload the 2-minute file to Avon & Somerset police and leave it with them to decide what to do. It's not for me to grab the phone or cause criminal damage or alarm. Half the time the driver is so engrossed they never notice me at all.
Some of the road on my way home is packed with queueing drivers eager to join the M5 a few hundred yards ahead. I have reported many who I have seen phone-in-hand driving off onto the motorway. This is a habit they would do very well to break before they injure someone or themselves.
After discussing how common distracted driving is on our roads with Nazan Fennell, the mother of Hope who was crushed to death by a phone-using HGV driver, I decided to report every phone-addicted driver I could.
https://www.cyclinguk.org/article/campaigns-guide/inquest-opens-teenage-cyclist’s-death