If you’ve used free wi-fi in San Francisco, there’s a good chance you’ve used Zenreach and just don’t know it yet.

The company, until now, has flown largely under the radar, because they wanted to amp up their business quietly for competitive reasons. And they’re finally ready to announce themselves and their new $30 million Series B funding. (Their previous $20 million in funding was super hush-hush). They are also welcoming billionaire investor Peter Thiel to their board.

An enterprise software startup, Zenreach provides wi-fi hardware to restaurants and coffee shops on a monthly subscription basis. They also help them with email promotions, using the address they signed up for when they logged onto the wi-fi. (They insist that they’ve built up firewalls to make sure their public wi-fi is extra secure).

Zenreach said it provides an important metric for the small businesses, which they are calling the “walk through rate.” Basically, Zenreach lets the shop know every time you walked back in. (Because once you’ve logged onto wi-fi somewhere, cell phones will default to selecting that wi-fi the next time you visit).

Zenreach “builds them a set of tools and platform entirely around their needs,” said Jack Abraham, founder and CEO. And they’re “helping power this free wi-fi wave for consumers.”

While apps like Yelp and Foursquare are trying to help small businesses with some of the same things, Abraham believes Zenreach’s “merchant-first approach” will help them in the long run, since they didn’t start out as consumer-focused services.

“Their metrics are really extraordinary,” said Joe Lonsdale, general partner at 8VC. They are an “amazing team and just a really big space” and doing “a lot better than anyone expected.”

Other investors include Bain Capital, SV Angel, Felicis Ventures, SoftTech and Peter Thiel’s Founder’s Fund.

Zenreach has grown to 150 employees in about three years.