Do you normally ride with your high beams on? If so, then the passing switch would not work to turn on/off you new aux lights. You would have to flick you headlights from high to low to high to activate the autoswitch.
I think it looks like a neat solution if you just really don;t want to add other switch to your bike. I've seen similar units that are designed to operate your garage door opener. Personally, I'd probably just follow Andreas' lead and add the bar mounted switch.
BTW, can you share some info about the landing lights you're using?