Gravy Analytics has an intriguing business: they build a huge database of real world events, like a yoga class, wine tasting, or real estate open house, and then uses location information from mobile app partners to identify the devices that attended. This information can be enhanced with demographics and then sold back to event organizers and offered as audience segments to mobile advertisers. Of course, no personal identifiers are attached and, when I asked, the company said no one had ever raised any privacy concerns. The company says it tracks one million events each day, 240 million mobile devices, and 15 billion daily location signals. It just raised a $7.7 million Series B, bringing total funding since 2011 to $21.7 million.