Some want to bake them. Others prefer to freeze them. Still others dehydrate them. Inventors will try just about anything to kill bed bugs, those nasty, reddish-brown, blood-sucking parasites that are the worst nightmare of many hotel guests.America’s obsession with bed bugs has led to a rush of entrepreneurs seeking profit from exterminating them, and about 75 companies gathered this week in hopes of launching the perfect beg bug killer.