A walkie-talkie (a.k.a., two-way radio) that guarantees reception in the forest? Easy. In your dreams.
Such a creature does not exist. Wireless radios are line-of-sight, easily flummoxed creations, and who knows what they will do in the hills. As regular readers know, I spent a number of years as a search and rescue volunteer. We had radiosexpensive radios, and lots of them. And guys assigned to haul repeaters to hilltops in the hope of extending the signal. For all of that, we might as well have carried reels with ten miles of string with an empty tin can on each end.
What you can do is buy one of the many models out there, and hope for the best. Motorolas Talkabout MR350R radios are as good as any$90 for a pair, good on both FRS (Family Radio Service) and GMRS (General Mobile Radio Service, for which you will need an inexpensive FCC license), with a range up to 35 miles...in ideal conditions. Otherwise, if you cant see the person whom you are trying to speak with, you likely will not hear them either.
Fact is, ski areas are pretty good for these things. Theyre generally open, and youre apt to have your party in the same basin. Better yet, TELL them to stay in the same lift basin. They go over the ridge to the next one, they might as well be on a different planet.