If you have watched technology coverage on YouTube, you are probably familiar with EightSleep. For those unfamiliar, it’s the water-filled mattress cover beloved by many famous millionaires and billionaires — everyone from top YouTubers to Elon Musk owns one — which connects to a small machine on the floor, adjusting the bed’s temperature as you sleep. If you like your bed cool, you can set it for cold; and if you like a toasty warm bed, it can do that as well. If you want the temperature to vary through the night to account for changes in your body temperature, you’re in luck. Additionally, if your partner has a different body temperature than you, you can control each side of the bed individually.