I recently had a project where I needed such a sensor, and I picked up a TF-MiniS, which is a popular IR distance sensor. They aren’t very expensive, and they work serial or I2C. So how did it do?

Here’s what we know about the MAX30105 air particle sensor. There are three LEDs inside this chip (red, IR, and green), and an optical sensor underneath a piece of glass.

Researchers have developed a smart sensor for DARPA that’s capable of identifying infrared -- without having to have its own power source.

This clever hack projects infrared dots onto the wall so your Wiimotes work without the Wii IR sensor bar. If you're unfamiliar with the setup of the Wiimote, the design is simple.