This is actually a good idea. ET Water was certainly ahead of the curve with the Hermit Crab. It is limited to the controllers with remote ports unless the panel can be replaced with one of theirs. Not all controllers have remote ports. The subscription fee is a bad idea even though I understand there are costs involved. Customers do not want any more fees.
Using sprinklers is costing them enough as it is, especially if they are using more than they need. I wonder if sprinkler system owners ever thought that the cost of maintaining the system and watering the lawn would cost them so much. It is an on going cost unless the system is just shut off completely.
As for Hunter's Hydrawise, they also want to charge you a fee for using a personal weather station in the area around your house. You can subscribe to one of the two closest airport weather stations, but you have to be on the Enthusiast plan to get stations closer to your location. No one wants an extra monthly fee.
I do agree that not all end users want to replace the whole panel. The savvy smart controller customers like it, but there are some who like to have access to buttons and a display.
Especially, the new home builder sprinkler companies. They want what is cheapest, easiest, and quickest. The companies use subs and they aren't necessarily the most knowledable about the latest, greatest, or most efficient. I mean, some subs use VAN nozzles on all the new systems because using fixed arc nozzles means they have to think and look in more than one bag to find the right nozzle!
Sorry about that little rant.
This is a good topic. I like the idea.