Something interesting about this project is the UI view is shared by all who view it. For example, imagine two people (two gardeners :) both pull out their cell phones and connect to the WiFi access point and browse to http://10.0.0.1.  Both users will see the same UI state.  The real state is stored on the Raspberry Pi; the UI is just a view of the state of the system, so it makes sense both would see the same view.  It's true for user input.  If one user clicks a checkbox, both users see the update.

If you want to try this out without building the whole system, open the demo in multiple browser windows.  You can do this from multiple systems, if you want.  Now start pushing buttons and notice all views are synchronized.