BP Search by Zip Code?

I'd like to allow my members to search via a proximity zip code, meaning within 5 miles, 10 miles, 20, miles, etc.. I searched BP plugins but have yet to find one that has such functionality.

Is this not one of the most important aspects of a community? It's great to meet people online but connecting people in the real world is where real value comes from. I'm guessing this would involve a zip code database but isn't that included with MarketPress?

Not sure why no one has done this yet...