Wall push-ups are a good way to get more upper-body exercise when you may not have time for floor push-ups, or maybe you're not so great at floor push-ups. They benefit chest, shoulders, arms/triceps, and core muscles. Step back just a little (safely) to "lean into the wall" more, and make the push-ups a bit more challenging. If you need to protect a wall from natural oil from your hands, try wearing non-slip or rubber gloves.
When I go grocery shopping, I bring my own bags. If I only have one or two bags, I leave the cart in the store and walk to my car (which I try to park far away from the door to try to sneak in a few extra steps). While I'm walking, I use the bags as weights and do a couple of reps of bicep curls.
In high school, I played volleyball. I never forgot how my arms hurt when coach made us do "sets" against the wall, 100 at a time. It occurred to me 20 years later, that I could get a volleyball and do them on my own. I do 100 sets during the commercials every evening. It's fun for me.