I would definitely buy this for my kids when I become a father

Little kids get tired very fast and also have a very short stride. This is ideal in a crowed area or when you have a hilly route because you always know where your kid is and can get from point A to point B quickly. You see it far too often, the parent pulling the kid along because the kid can't walk the same speed as the adult. This is also much safer, try to grab the kid and you get a full grown adult's weight barring you.

I was a kid, I walked everywhere. What's next teleportation devices so people don't actually have to walk anywhere?

Yes it is

Liev Schreiber :)

No worse than a backpack. Kid's don't weigh that much, your legs will give out before your back.