I propose to have some sensors which would measure the humidity of soil in home use. This will be of some help to those who have a lot of indoor plants. Different kinds of plants need to be watered with different frequency. That is why such sensors could be programmed to the level of humidity needed and give a signal if the time for watering came. In this case there is no need to check the humidity of soil with your finger every day, which is not very scientific. And no danger of overwatering!