I've looked at a few top apps, and I thought "Street Food App" is a top developer. Problem is you would have to convince them to open in your city, but the fact that you are in Denver seems like you wouldn't have that tough of a challenge.
Toby is the point man, who I've been talking to. He might be a one man show, I am not sure. http://streetfoodapp.com
One of my major issues with some of the cart apps I've reviewed is they are too cluttered and hard to navigate, or they don't have decent connectivity to other social media links that can be useful for self promotion.
I do want to check out Roaming Hunger. I have not looked at that one yet.