I’m a GeoDrops kick-starter backer (as are some Rachio employees), so I know there’s some interest in the community ( How do you interact with soil sensors? - #38 by cchrisgates for example)
I’ve connected my 4 GeoDrops sensors to my Home Assistant (GeoDrops exposes sensor data via Google BigTable), which then uploads the moisture data on a per-zone basis to Rachio. It’s been working well this winter, although I obviously am not driving watering decisions through it yet 
GeoDrops is working on their official IFTTT integration first, then I think a direct Rachio integration is next on their integration list.