All flood sensors work the same way. They have two or more leads that, when they contact water, detect higher conductivity. Then they set off an alarm and/or send your phone an alert. What distinguishes each device from its competitors is the extra features.

The Honeywell Lyric Leak and Freeze Detector is one of the most expensive flood detectors out there. At $80, it measures temperature and humidity, works using Wi-Fi rather than a smart-home hub, features a loud alarm, and has a cable of twisted leads that extend the sensing range of the device considerably. Sadly, however, the Honeywell isn't waterproof and doesn't work with many other smart-home gadgets.

The D-Link Wi-Fi Water Sensor, at $60, doesn't rely on a smart-home hub like most of its competitors do. It also features a cable of twisted leads like the Honeywell Lyric. Its real strengths, though, come from not relying on batteries and working with IFTTT for cool smart-home integrations.

The Everspring Z-Wave Wireless Flood Detector costs $40 and features a long, wired probe. Unlike the D-Link or Honeywell, this wire only has probes at its end, so it doesn't sense floods along its length.

The Aeon Labs Aeotec Water Sensor is $35, but is otherwise almost identical to the Everspring. It's perfect for measuring water levels in a sump pump, but it won't work well under a sink or for monitoring larger areas.

The SmartThings Water Leak Sensor is an affordable $40, but it has very few extra features to speak of. It works effectively, especially if you already use the SmartThings platform.

FortrezZ's Water and Temperature Sensor costs $48 and measures temperature. But it doesn't work especially well, and it has no audible alarm.

The Fibaro Flood Sensor is one of the best Z-Wave dependent devices on the market. It measures temperature, alerts users in case of tampering, and even floats in water. It costs $60.

Every flood sensor offers users different abilities. For more in-depth analysis, check out this buying guide.