The Thirsty Light is a digital plant moisture sensor that blinks an LED to alert the user when it is time to water a potted plant. It is designed to be unobtrusive when left in the soil of a plant, where it continuosly monitors conditions, testing the moisture level once per second.

Thirsty Light can sense 5 different levels of dryness, causing the light to blink faster as the soil gets dryer, increasing the urgency of its call to action. When it reaches the fifth level, "completely dry", the device goes into standby mode to conserve electricity, emitting a double blink every 3 seconds. There is a low-battery mode as well: a slow triple blink. The Thirsty Light comes with a comprehensive and informative user and watering guide.