Adding new device types to nymea is done with plugins. With some development skills and if the hardware is not vendor-locked, it's rather straight forward to add such a plugin. This post shows one approach to create a plugin by the example of the Xiaomi FlowerCare sensor.
The internet is full of tutorials on how to read digital and analog sensors, now it is time to do something useful with this data.
Smart Irrigation is not only about saving water or having healthier plants. It is mostly convenience that convinces the consumer to buy a smart irrigation system. Most people don't want to have to worry about their garden. They just want it to be a place to relax.