Yes, Fox 40 whistle
and a signal mirror. Yes, both have been used to signal that knothead trail runner before he could disappear into the distance... diferent knotheads, different trips.
Whistles can be blown on forever - yelling for two hours, you lose your voice. In some conditions, you can't hear either until you're almost on top of the person. If I were stuck in a canyon with two broken legs I'd want a whistle, some fire starting materials, a PLB, and water. If the helicopter can't land right next to me the PLB isn't the only thing I'd need. Being holed up under tree cover means you're going to have to have something to signal rescuers as they come closer. Thinking that the GPS coordinate will be accurate down to the meter isn't a mistake I'll be making.