Neat stuff. It's a sensor that measures actual evapotranspiration in the field, which is essentially how fast the leaves are losing water. This can be very useful in deciding how much irrigation is needed so that the plants are not unduly water stressed. The link to their website in the article turns out to be broken, but it leads to https://www.tuletechnologies.com/.
There were a number of interesting things in their FAQ that weren't mentioned in the article. The main one that jumped out is that contrary to the article, the cost is not $1500 per sensor, but is a $1500 per season subscription, with the use of the sensor being included. That's an interesting model. And I greatly admire that they are being so clear about pricing on their site.
Also from the FAQ:
How do we know it works?
We use a recent innovation in atmospheric science from the
University of California at Davis to measure Actual ET.
This innovation was validated against lysimetry and eddy
covariance. From a technical perspective, Tule uses the
Surface Renewal method to measure how much water vapor the
wind is carrying away from the field. If you’d like a more
in depth look at the technology, please let us know.