My son had one of those gizmo watches around maybe age 8 or so. We switched him to a flip phone a few years later and then he got his first smart phone last year when he turned 15.
13 for both of mine.
My plan is to get them one when they’re at an age where they’re going out places with their friends. And it’ll be just a flip phone for emergencies, no smart phones
11 as he was spending an hour travelling to school by taxi plus being left at home for short periods while I took his sister to things like gymnastics and we don’t have a landline. We started off with a basic brick which didn’t have any wifi however he never used it once the initial excitement wore off.
I won't be getting her a phone until she is in highschool but I do plan to give her like a gab watch with loafs of safety features when she is probably in kindergarten/1st grade but it'll be for when she is with her dad