Eight Sleep is an American sleep technology company that makes the Pod, a connected cover placed over an existing mattress. Water channels can cool or warm each side of the bed separately, while built in sensors track sleep without requiring either sleeper to wear a device.

How it works
A bedside hub circulates temperature controlled water through the cover. Pressure and movement sensors detect sleep, breathing and heart related signals, while room sensors add temperature and humidity. The system uses these patterns to adjust each side through the night. The app shows sleep reports, temperature changes and alarms.

Key considerations
The Pod is an expensive system and many automatic features depend on a paid membership. It also relies on power, water circulation, software and connectivity, although basic offline controls have improved.