That's Firewatch, a nifty-sounding PC game just announced by indie outfit Campo Santo. They say you'll play as a fire-lookout in the Wyoming wilderness, drawn out of your watchtower by strange events and tethered to humanity only by the voice on the other end of your radio.
More info at the game's official site.
The full official description:
In Firewatch you play as a man named Henry who has retreated from his messy life to work as a fire lookout in the Wyoming wilderness. Perched high atop a mountain, it's your job to look for smoke and keep the wilderness safe. An especially hot and dry summer has everyone on edge. Your supervisor, a woman named Delilah, is available to you at all times over a small, handheld radio—and is your only contact with the world you've left behind.
But when something strange draws you out of your lookout tower and into the world, you'll explore a wild and unknown environment, facing questions and making interpersonal choices that can build or destroy the only meaningful relationship you have.