The "mystery-adventure-walking simulator" Firewatch [Official website] has been released on Steam.
Set in the year 1989, you play as a man working as a fire lookout in the Wyoming wilderness. Your only contact is with your supervisor - available at all times over a handheld radio. How you choose to interact with her, or what you report in your walks builds or breaks down the only meaningful relationship you have.
I haven't had a chance to play this yet, but I hope I plan on it soon. I like a good story, and from what I've seen the voice acting is also top notch.
Firewatch is available now on Steam for $19.99.
There's no recent trailer, so I'll just have to go with this one from 2015.