"... the mix of men and women, their ages — and to make all this information available live via an iPhone or Android app. Privacy advocates are unimpressed, though, as the only hint that people are being monitored is via tiny stickers on the windows."
Sorry, I think this is a great idea. I checked out the website, and it's not just 20 bars in San Francisco. They've got lots of cities, including Madison, with 6 bars. I think it's great to be able to see which places are crowded, what the sex balance is, and what's the average age of the men and, separately, the women. This is very helpful information for customers and for businesses. I approve!
As for privacy, people are out in public, and they know they are being looked at. Even though cameras are being used to capture faces and the faces are analyzed for sex and age, no one's picture (or name) goes up on the website. It's simply technology, cleverly applied for a useful purpose.