MSI Afterburner or EVGA Precision X. Both are essentially the same(made by Unwinder the maker of RivaTuner), and support on screen display while in games. Though you have to enable monitoring for the Core Clocks or whatever they are calling it this week.
Just put a check next to the ones you want displayed. And select down towards the bottom "Show in On-Screen Display" for each one you want on screen.
It will give you this + or - the things you want monitored.