The biggest use for me is turning from a static position, e.g. left from a cross-street, having started this after I made a left turn but was t-boned, mind you I've always been religious about seatbelts, checking turns (left-right-left), etc. When doing a static turn I will point-and-call left, "Clear Left," point-and-call right, "Clear Right," point-and-call left again "Clear Left," then with both hands on the wheel say "Go."
I will look-and-call for lane changes, pretty much as you would imagine look over the shoulder and "Clear Left," then "Turning." Same goes for right. For me it is more action oriented, to make sure I've assessed the area for issues. I haven't done anything like call outs for threats, but now I'm kicking myself for not thinking of that. I already do that religiously in FPS games, I could see how doing that would be good to get and stay in the habit of active scanning, "Pedestrian crossing, two o'clock." Might have to try that one out too, after all my friends will love that development :)