If I went this route, it would make more sense than a timer, since there are many times we do get plenty of rainfall, but it would be nice to have an automated system kick in for times (like now) when it's dry, but avoid wasting water when it's not necessary to water.

I know these exist - what are some good ones? Do they have to be calibrated, etc?

The rain sensor makes sense on the surface, but theN I imageine that "rain" it is sensing that shuts off the sprinkler could be a 4 minute light shower that doesn't even penetrate the surface.

So is a buried moisture sensor a better option?

How the UgMO ProHome Works you may ask? It is a cost-effective, wireless water sensing "watchdog" the smart sensors are placed underground in each sprinkler zone to measure soil moisture and temperature at the root level (the most important part of the plant) up to 12 times an hour, 24 hours a day, 7 days a week, 365 days a year. These sensors will wirelessly transmit data in real time on a zone-by-zone basis to my UgMO ProHome base station that was installed next my existing irrigation timer. Acting as the "brains" of my irrigation system, the base station determines when the grass and/or plantings have reached their optimum moisture level. If the ground is sufficiently moist, UgMO will automatically interrupt the sprinkler in that zone, turning it off before any water is wasted. It will still work even when it rains. Plus it has a zone manual overide"Plus Not only is this an easy install for contractors, but it is a simple technology for me too. So i Set it and then forgot it, and then i watched my water and $ savings accumulate. I.m.o it saves alot if hassle. The only drawback to the installation is i had to dig up slices of turf in my beautiful Bermuda lawn to install the sensors.

How the UgMO ProHome Works you may ask? It is a cost-effective, wireless water sensing "watchdog" the smart sensors are placed underground in each sprinkler zone to measure soil moisture and temperature at the root level (the most important part of the plant) up to 12 times an hour, 24 hours a day, 7 days a week, 365 days a year. These sensors will wirelessly transmit data in real time on a zone-by-zone basis to my UgMO ProHome base station that was installed next my existing irrigation timer. Acting as the "brains" of my irrigation system, the base station determines when the grass and/or plantings have reached their optimum moisture level. If the ground is sufficiently moist, UgMO will automatically interrupt the sprinkler in that zone, turning it off before any water is wasted. It will still work even when it rains. Plus it has a zone manual overide"Plus Not only is this an easy install for contractors, but it is a simple technology for me too. So i Set it and then forgot it, and then i watched my water and $ savings accumulate. I.m.o it saves alot if hassle. The only drawback to the installation is i had to dig up slices of turf in my beautiful Bermuda lawn to install the sensors.