Months later, pulse oximeters are easier to procure -- they're in stock at some stores, and there are still some decent deals to be found. Whether or not you actually need one is a different story.

A pulse oximeter is a device that clips on your finger, toe, or earlobe to measure blood oxygen saturation. Here's how it works and how to read it.

Although a new study showed the devices are more error-prone in people with darker skin, doctors say they are still useful for anyone monitoring Covid-19 at home.