Soil Humidity Sensor for Brown Thumbs

After having drowned several plants, I finally came across a very useful tool for brown thumbs like me: a soil humidity sensor.
You just have to stick it in the soil and read the information on the meter, you will immediately know whether you the plant needs watering or not.
I've tried it with several plants including my new lavender one and it really works. I hope this helps me to keep them alive longer.