The Gyro Ball is made of a rubber shell filled with a stiff foam that holds a motor motionless and allows it to turn a weighted gyro scope freely when a button is pressed. The gyro spins and causes the ball to try to spin the opposite direction (conservation of angular momentum). If the ball is on the ground this will cause it to start rolling on its own.
The idea is for the child to be mystified by the ball that begins to roll when a button is pushed or resists being rolled in certain directions (parallel to the axis of the gyro's rotation). When thrown the ball would exhibit strange spin and erratic flight, though when the motor is off, the ball would be perfectly balanced and behave completely normally.
The Gyro Ball being made mostly of foam and rubber and so presents very little danger. Hopefully, it will be water resistant due to the rubber shell. If disassembled it may be dangerous for younger children. The motor and gyro would be assembled and contained in a plastic shell and cast inside a foam core and covered in rubber.