Here is a cool STEM kit that comes with everything your kids need to build new things and control them from their Bluetooth device. The littleBits Gizmos & Gadgets Kit 2nd Edition can be used to build all kinds of bots. It comes with 13 bits and 56 accessories. You kids get to work on a prank box, dancing light, spin roller, inchworm, and other fun inventions.
This particular kit comes with a buzzer, DC motors, light sensor, bargraph, servo, and other components. An invention guidebook with step-by-step instructions is also included.