My mother was worried that my neice could put one of the phone charger cables in her mouth now that she is crawling around. She asked if I could come up with something to cover the end of the plug so she couldn't get it in her mouth. I'm not sure of the exact dangers with that, but I can't imagine there is anything good about putting the plug in your mouth and it sounded like something fun to design. I wanted something that stayed on the cable and couldn't come off or get lost.
What I came up with is a cover that slides onto the charger cable, and a small ball that is clamped onto the end of the cable near the phone plug. When you are done charging you just slide the cover over the end and the ball snaps into place and holds the plug inside the cover. To release you squeeze the sides of the cover and push the cable out.
2/9/20 On the suggestion from a member of the 3D Printing Useful Things Facebook group, I have added some holes through the ball portion that attaches to the cord. This should help eliminate the possible choking hazard for the ball on the cord when not in the cover, since it is no longer solid.