You can check http://coingecko.com it's a pretty nice and resourceful site. It's still in Beta and it doesn't have exactly what you are asking, but maybe you can email them, like I said, it's still in Beta.

If you plan to start your own, maybe just a one-page website, with just these two values would be enough. Nice, simple, clean and minimal.
Where do you plan on getting the data from?