I've been interested in self-experimentation recently, inspired mainly by Seth Roberts (who kept track of his sleep), Ramit Sethi (who tracks his spending), and Ben Franklin. I've told some of my friends, and they told me that I was a nerd, and I told them to tell me something over which I don't already cry myself to sleep every night.
But now I want to add something else. Since I plan to live forever or die trying, I've thought that maybe I could track some facets monthly as well as daily. So I'd have a day every month that I list some crucial measurements. So far I've got weight, tentatively mile time, and how long I can hold my breath for. Anything else? My goals are: easy to measure, take 0-10 minutes, and interesting. I tried subjective happiness, but I gave myself 5/5 three weeks in a row and decided it was silly.
It's my life, but you can be a part of it.