Allow the user to stipulate "must hit spots" before choosing a route.
I am at the grocery store, and I need to drop cloths off at a dry cleaner, and pick up lunch at a "Panera" on my way home. When I set my destination I am presented with 3 routes that pass by a "Panera" and a Dry Cleaner. I then choose from those three.
Without this functionality I have to choose a route and then hope that these things are on my way.