I think you pretty much just called it there - the main thing you can do with a bar is curls, awkward as it is. You can also do reverse forearm curls and ordinary forearm curls, though, and you can do laying down tricep skull crushers (what I call em, Idk if they have a more official name) so at least you can hit the whole arm.
@ the workout app - I might try that, looks neat.
I recorded my workouts for a very very long time, but in the end I decided that it was more of a phase on the road to fitness discipline, not an end. It's tremendously helpful to track your progress, but IMO it's only necessary for awhile, until you get a solid enough set of personal expectations of your body that you can figure out on the fly what is, and isn't, a challenging workout for yourself. Beginners who can't keep track of what muscle groups they've done recently, what type of set/rep structure they've been doing or want to do, or how much weight they max out on, can definitely get quite a bit of discipline and organizational efficiency out of recording their workout in real time.
Eventually though, I felt a little trapped by it. I felt tied to my notebook, and less flexible in my routines and my speeds by being obligated to stop and record everything. It most definitely serves a purpose, I just no longer believe that one cannot enjoy a productive, efficient and disciplined workout without it. In fact, I felt a little liberated by ending my use of it, because any time I feel like I'm going too easy on myself, I just say "screw it, I'll do quads and calves today too", or, "I'll sprint between chest workouts", or "I'll do a crossfit abs routine until I curl up and cry like a little girl"
and I didn't feel that kind of flexibility lent itself to a notebook-recording workout mentality.