I've been climbing for years outside work and I feel like it's a great hobby for programmers. It gets you outside and you are essentially problem solving. I found my side projects (video games, rpi things, fun programming) are much more productive when I spend time climbing.
I also found it helps me not think about work. Before I started climbing, I would think about my next work day non-stop which was totally counter-productive. I would over think things and then get stuck in a rut for weeks at a time. I now care less about my work when I'm off and I think it's actually made me a better employee.