Rocket Ride Miniature on-board live video system lets you go along for the ride in a toy rocket. Other instruments measure the g-force, velocity, and wind speed. All these are beamed by radio back to the ground station, where kids can track the telemetry to improve on later flights. That way, it wouldn't end up on the neighbor's roof. Could also be outfitted with a camera, altimeter, or other sensors to record the flight.
Similar ideas apply to boats and cars.
They can all also be flown semi-autonomously or fully controlled by the children as they get more experience.