Here is another robotic arm kit that teaches your children a thing or two about technology and building things. The Thames & Kosmos Mechanical Engineering Robotic Arms kit lets you build 6 different robotic arms. Its parts are controlled using a pneumatic system.
Pistons are used to move the grabber claws and other parts. The kit comes with a 32-page instruction manual and over 204 parts. Costs under $47 at this time.