The GrowProbe is the new indoor plant tool that allows you to easily check the moisture in the soil at the bottom of the pot. This is where checking the moisture counts when it comes to watering.
It has four notches along the body that when pushed vertically into the soil and pulled out again collects the samples throughout the soil.
Using these samples, you can feel the soil and decide whether the plant needs to be watered. If it's moist or wet, check again in a few more days, if it's dry it's time for a water.
As well as preventing you from overwatering, it also aerates the soil! This is great for improving drainage and root health.