The MPU-6050 is an InvenSense sensor with a MEMS accelerometer and a MEMS gyro. It's available as a breakout from SparkFun for ~$40/board, but I needed at least 5 of them. Ebay/amazon/aliexpress was happy to help! These other breakouts were mega cheap and so far I've only had one failure out of 6. Not bad for the price.

The MPU-6050 communicates over I2C, so we need to be fancy with the addresses if we're going to read 5 at a time. I ran into this issue with the IR temperature sensors for the Starfish Cat, and solved it by manually changing the addresses on the MLX90614 and editing the library to allow for multiple addresses. It's not as easy to reprogram the address on the MPU-6050, but you can shift the address dynamically by writing the ADO pin low (0x68) or high (0x69).

If you attach ADO to your digital pins and only turn one on at a time, you can scan through the sensors to grab data before switching the address again. This is a recommended trick for the MPU-6050 on the Arduino Playground. Your granularity will leave something to be desired, but if your goal is to read extreme motions like finger strikes, then you’re probably okay. Here’s an example of this method employed with the Particle Photon.