The Thirsty Light® is a digital soil moisture sensor that blinks an LED to alert you when it is time to water a potted plant. 

Designed to be unobtrusive when left in the soil of a plant, it continuosly tests the moisture level once per second.

Thirsty Light senses 5 different levels of dryness and uses blinking patterns for easy recognition:

No blink - Moisture detected
Slow blink - Starting to get dry
Medium blink - Dry
Fast Blink - Very dry
Double blink w/ pause - Completely dry/Standby
Low battery mode - a slow triple blink

As the soil gets dryer, the light blinks faster! When it reaches the fifth level, "completely dry", the Thirsty Light goes into standby mode to conserve electricity, emitting a double blink every 3 seconds.

The soil probe is corrosion resistant brass, and the Thirsty Light has a tough ABS plastic casing. It has an On/Off switch to conserve battery life when not in use.

The Thirsty Light uses two replaceable 1.5V batteries (included). Comes with a comprehensive and informative user and watering guide. Backed by a 30 day manufacturer's warranty.

More info (PDF format)