We currently have a feature called shared access:
If you can wait a bit, we will be re-releasing a feature that used to be called landscaper access. All you need to do is enter an email address, we send a one-time expiring link, and the landscaper can only control zones on/off. They do this through a webapp so no need to install a native iOS/Android app, or even sign up for an account. This will be released soon.