While it blinks if your plant needs watering, mine only started blinking when I moved it a little in the pot. In other words, it doesn't work unless you remember to wiggle it a little to check if your plant needs watering...
That kind of defeats the purpose unfortunately, since you might as well water it if you've remembered to wiggle the sensor.
Jasper Smits, Netherlands - 11th June 2012
Firebox says: That doesn't sound right Jasper, you may have a defective thirsty light. Drop us a line with your order number and details and we will look into this for you.