I built a $4 temperature sensor that works with every smart home app

Walk into any electronics store, and you'll find plenty of temperature sensors priced anywhere between $15 to $50. Even if you get past the price and buy a fancy one, you'll be disappointed to know that they often work in just one ecosystem. If you pick the wrong one or you want another option, you're looking at some very expensive paperweight.

Read the full article at the source.