After a few cosmetic improvements with the augmented reality functionality, my tip calculator/foursquare client/yelp review search app Gratuitous has been approved for the Windows Phone Marketplace. Version 2.0 should be visible and available for download sometime in the next 24 hours.
Remember, it is not enough to just have a device running Mango to view the augmented reality functionality. Your phone must have either a gyroscope (such as the HTC Mazaa) or the necessary compass drivers to enable the Motion API. My understanding is that those compass drivers will not be available on first gen devices such as the Samsung Focus, HD7 and LG Quantum until build 7720 is released by the hardware manufacturers and carriers.