If you choose to buy your child a scooter like a Razor please be aware that your child should always wear a helmet while riding it, as well as wrist-guards, elbow pads, and knee pads. The same applies to roller-blades, skateboards, and Rip Sticks.
Also, to consider is a sports guard for your child’s mouth. I know of a child who was riding on a Rip Stick and fell on his face. He broke a front tooth – an adult tooth – and now needs all kind of expensive dental work. Better to spend the money to prevent the injury than to have to go through all the pain and running around to different doctors afterward.