Yep, just a regular climbing carabiner from the days when I used to climb (before children -- someday one will be my ropegun...). I've been meaning to order a leather fob from Zissou if he's still making them...I'm always juggling stuff so I need to have the keys handy. And jamming a ring with a bunch of keys into jeans that fit the way I like them to is hazardous to my femoral artery.
I do keep my iphone in my front pocket ... but that's not really a good solution: I'm paranoid about sitting on it so don't keep it in my back pocket, but also worried about slamming into a subway turnstile in my front pocket...plus getting weird fades...file under: first world problems, I guess.