I have a couple of rentals, and do not use any plans like this. When a tenant calls me with a problem, I usually go over and have a look and if it's not something I can fix I call a repair person right then. Furnace repair people are always available on short notice, but plumbers usually schedule for 2-3 days out unless you have an emergency.
I don't see the advantage of paying someone to call a repair person for me, except that it spreads out the cost over every month instead of hitting you with big bills for occasional repairs. I maintain enough of a cash buffer in my rental accounts that it's never been a problem.