Fibaro FGBHFS-101 Flood, Water & Temperature Sensor Homekit enabled Price: $66.99 (as of 04/08/2023 12:15 PST- Details)

The FIBARO Flood Sensor is Apple HomeKit enabled water leakage detector that protects your home against possible water damages
Get immediate notifications on your iPhone whenever water leakage incident happens in your home (Apple TV or HomePod required, if your iPhone is out of Bluetooth range)
FIBARO Flood Sensor is also equipped with visual and sound alarm , so it works as stand alone device