Rode up behind a car doing a 10 point turn near a junction and waited patiently for it to finish. Then it stopped at the junction. So I waited and waited, and shouted, rode up to her window to find her fiddling with her phone. Shouted, and rode on, then when she drove past me a bit later I made the 'put the phone down signal', because she was still on it. Then when I rode past her again as she sat waiting to turn right, still looking at it instead of paying attention to the road.
(A few weeks ago I was sitting on the bus, looking backwards, and there was a girl in a BMW in traffic who I estimate spent 95% of the time behind the wheel playing on her phone. It amazes me.)