Open University discusses a device they built called SenseBoard for a teaching module designed more for educators in mind than hobbyists — a handy board, also interesting in that it is several orders of magnitude more expensive that the Pi you might hook it up to. From RaspberryPi.org:
The Open University faced the same problem when we started developing a new introductory module called ‘My Digital Life’. We wanted to integrate computing hardware into our teaching, but nothing on the market was suitable for complete newcomers.
So we developed our own device – the SenseBoard – and the Sense programming environment that drives it. The Senseboard is about the size of a Raspberry Pi, and comes with inputs and outputs including a slider, noise sensor, and IR detector. Input sockets allow other sensors to be added. We supply light, heat, and motion sensors, and you can make others that act as variable resistors. Outputs include a bank of LEDs and plugs for stepper motors, servo motors, and an IR LED on a lead. The SenseBoard simply plugs into a USB port.
The SenseBoard gets students, most of whom are new to computing, quickly building physical devices that have real, immediately visible effects in the real world. Based on the Scratch programming environment, Sense makes this possible by including blocks to interact with the Senseboard, as well as reading and writing over internet.
When the Raspberry Pi came out, it seemed like a marriage made in heaven. A cheap, simple computer together with a simple, robust physical interaction board opened up many possibilities.
However, getting Sense working on the Raspberry Pi wasn’t straightforward. Sense, and Scratch, are built on an old version of Squeak. We had to go through some shenanigans to compile a Squeak virtual machine for the Raspberry Pi’s ARM chip, and then persuade it that serial devices could exist on USB ports. But we got there in the end!