But my child always wears hi-vis! He even has hi-vis pyjamas, in case a bad billy burglar (could also be bobby burglar) steals him while he's sleeping, or he sleepwalks and trips over a self-inflating toy on the floor. Needless to say, he has a helmet permanently on his head for the same reason. There's a special model with a detachable top part for washing his hair. Did you know that 17,698,342 children got shampoo in their eyes while having their hair washed last year in Greater London alone? So obviously he has a visor on this helmet. I mean, it's only fair, think of the trauma otherwise.
Road safety is taken care of by transporting him in a large flo-yellow motorised baby buggy. We've invested in an airport-tunnel style chute to get him from this to the front door. So much danger on the pavement. Shame he's forgotten how to move his legs, we did plan on him becoming a premier league footballer. Never mind, that nice Jeremy Carson Beadle man from the telly says he can be a racing car driver instead. So, that's our pensions sorted!
Seriously, I think this is not so much a "safety" device as a "tracking" mechanism, as suggested by PhilO above. "We counted them all out, and we counted them all in."