I am one of the folks that didn’t have much success with the WFM - inconsistent readings leading to exceeding threshold warnings, random zero flow errors, etc. Support was very responsive and helpful and we tried many different things to resolve the issues, but for my particular installation we were never successful. I ultimately disabled the notifications across my 12 zones.
On the topic of this post, I installed a Flume device.
It is wireless, and straps around the water meter at the street. No pipe cutting or anything. It appears to be very accurate thus far. They do not interface with Rachio, but do have an API. I hope that Flume and Rachio will interface with each other at some point. I realize that since the Flume installs at the main water input, you wouldn’t be able to isolate irrigation consumption from regular house usage, but I run my irrigation very early in the morning before we get up, so there wouldn’t likely be any water running in the house anyway.