Perfect for under and over-waterers alike, this handy tool lets you know whether it's time to water or wait! Simply insert the probe into the soil and it will give you a reading. There's also a handy list on the back of the box which notes some of the more popular houseplants and the soil moisture level you should be aiming for. Easy! 
 
The design is chic and minimalistic, with the reader in plain white casing.