An idea that tickled me enough that I had to implement it before I could go to sleep. LifeMeter will display a small meter on your MacOS status bar, similar to the battery meter, tracking your progress through your time on this planet.
Make sure to configure your birth date and life expectancy.
Download the latest release from the releases page, and drag it to your Applications folder.
LifeMeter uses a standard Xcode setup. Note there is a small embedded helper application, necessary for the "start at login" functionality.
If "Start at Login" doesn't work on your local dev box, make sure to read through http://stackoverflow.com/questions/27876046/error-when-enabling-auto-login-of-mac-os-app-using-a-helper