I call out "You OK?" I carry a pump (I have never figured out how to get them to do Schraeder valves, so I limit my offers of tire help to road bikes), tubes (same issue), patches, a few allen keys and not a lot else. Oh, and I always keep a few bills in my wallet. I've used as many as four to limp home with gaping rips in my tire. I should get back into having 8, 9 and 10 box wrenches on me or a small crescent wrench, but there are usually ways to improvise.
As for the rest, chain, cranks, spokes, etc., unless I have reason to suspect those items, I would end up carrying a lot of tools for things that cause me to walk very seldom. (And if I really get stuck, I carry AAA Plus for its bicycle coverage though I haven't used it yet.) Maybe I should get back into carrying my Leatherman, a really good tool but a real jersey pocket eater. My smaller and lighter Gerber is much nicer in my pocket but is only a toy.
Ben