Been looking at the wiring for these devices, that link into the wall switch. You rewire so the z-wave device controls the load, but the existing wall switch is wired into the z-wave device so the manual control is still available.
Say the wall switch is on, and you use the controller to switch the load off, the wall switch is still on the on (down) position. If you then want to manually switch the light on do you change the switch to 'up'? Like having a double switch arrangement with one at each end of a hall - it means that up-off down-on doesn't apply anymore and it toggles the load state? Or would you have to move the switch off and on again?