All you need is a phone line! All phone lines have a constant flow of voltage, around 40-70 volts (up to 100 volts when it rings!), but you can't just plug stuff into it and expect it to work.
Children older than 5 and more than 40 pounds must ride in a booster seat until the child is 8 years old or is taller than 4 feet 9 inches. Anyone over the age of 8 must be protected by a safety belt.
A backless booster. A booster seat is used to lift up a child and properly position the vehicle's lap/shoulder belts on children who are too small to fit the adult seat belt. Boosters are rated for use from 30-40 lbs to 80-100 lbs.