The DFRobot Boson Starter Kit allows easy connection of multiple sensors and other inputs and outputs, to the BBC micro:bit.
We were looking for a kit that would be easy to get working quickly for primary-aged teachers, and their students. The Boson starter kit came to our attention after some customer enquiries, and offers great expandability due to the simple plug-in interfaces. Using a standard micro:bit edge connector, setup is straightforward; leaving the micro:bit's microUSB port accessible for programming, while immediately adding useful features like a power switch and speaker (with volume control in rare cases those fun tunes start to get a little too repetitive ;) ).
There's a great range of colour-coded components that can be attached to structures with screw-in magnetic brackets that can also connect to Lego, or directly to a whiteboard. The system uses easy-to-connect leads that allow good flexibility for orientating components.
Documentation is clear and straight-forward, using the popular MakeCode.com editor, with many other components available for expansion.