He’s using an i2c temperature sensor , and we think the PCA9517 Level-Translating I2C Bus Repeater that makes it possible is a perfect match for the RPi. This is a Texas Instruments part.

I2C has a seven-bit address space, and you’re thinking “when do I ever need more than 127 devices on a pair of wires?” So you order up some parts only to find that they have one, two, or ...