Customized littleBits Wire
This project requires an extra output, so some soldiering will be required on your Arduino board to install extra pins. Plus one W1 Wire bit has to be cut and modified according to the picture.
Please do not do it by yourself if you are not a specialist. You may damage your bits.
Let me know if you have questions.
Assembly according to the pictures and program the software.
Fasten the bits on the board with rubber bands.