Someone in this forum once commented that the most useful smartphone app they could think of was not something with GPS capability to locate yourself, but something that would tell you why you just walked into this room!
I'm still only in my 60s, but I would find such an app to be extremely useful.
More seriously, I do agree that physical activity seems to be about the most useful drug we can take. My grandfather still took a daily half-mile walk in his 90s, and it seemed to do him a lot of good. He lasted until 96.
There was a local businessman in Cincinnati who maintained an office until his death. Every morning he would have breakfast, put on a suit, walk several blocks to the bus stop to catch the 7:30 am bus, and ride the bus into downtown. There, he bought two different newspapers and walked six flights up to his office where he read the newspapers, drank coffee, and chatted with anyone who cared to drop in. He went to lunch in a nearby restaurant, then took the bus back home. This was his routine until he died at either 100 or 101 (I forget exactly).
It seems that keeping your body as active as possible has the side effect of keeping your mind sharp as well.