[RobertT]

1 Depending on the cost, size and the cost would determine the usefulness along with features.
2 I spend a couple of hours a day watering in the outside and inside plants.
3 yes to problems over and underwatering
4 That would depend on sensor and operational / control options
5 A numerical display indicating % moisture would be best as I would be using it in soil, hydro, and bark mixtures
6 Yes but a solar cell to recharge the batteries would be a benifical item
7 Sensors should be as small as you are able to make them if using radio transmission to the controller then the controller size would not matter as it would not need to be directly in contact with the sensor unit and could be programmed with software and a laptop
8 It would be better if I could install it myself for home/personel use, but a professionally installed unit would be good for busisness use.
9 The value of the unit would depend on the features and ease of operation and control variables
10 I would like for you to look into flow control for each sensor as the different sensors could then be programmed for the type of soil or soiless medium it is used in and also to control misting systems for humidity.
11 Yes you may contact me again with further questions, T&E / demonstrations as I do T&E of products other than gardening ones as a part time job and would be glad to assist.