I think it would be profitable to write a smartphone app that takes the floor plan of a trade show or exhibition hall with the exhibitors' booths shown, allows the user to select the booths he or she wants to visit, and solves the travelling salesman problem. I wonder if it could be licensed to trade show organizers for big bucks by offering kickbacks on all the extras. The extras could include bribes from exhibitors for the heuristic to favor paths that go by them, or that get users to visit them ahead of their competitors, or that push promotions to users redeemable at the booth but only within the next five minutes, or that lets exhibitors buy a list of the names of everyone who selected their booth, or lets them buy a list of the other booths those people also selected, etc..