Cotap, a messaging startup co-founded by two ex-Yammer executives, came out of stealth last year with a very specific aim: using the boom in smartphone usage to break down communication barriers between “knowledge workers” chained to computers and employees who are front line, out in the wild, and directly interfacing with customers. Some three months after launching its first app, on iOS, Coptap is today announcing a new $10 million round of funding to build out that vision further, extending the app to Android and desktop, and hiring talent to build more features into the product, including its first tier of paid services.

As of today, Cotap has already signed up employees at 6,000 businesses to use its free app.

The Series B investment, which comes on top of a $5.5 million round last year, was led by Emergence Capital, with participation from Charles River Ventures. Both VCs were early investors in Yammer.

Cotap’s debut and growth are part of a bigger consumerization trend among enterprise software developers: taking cues from the apps we use on our smartphones, tablets, and home computers, enterprises are moving away from dry and cumbersome legacy products. Workers want apps that are easier to use and more engaging, and on the IT side, the company wants services that are easier to implement and manage.

That’s given rise to a lot of startups that are trying to tap into this trend to make basic apps for already-connected employees easier to use. (Incidentally, one of the startups in that space, Tomfoolery, appears to be getting acquired by Yahoo.)

Cotap, however, takes this concept and extends it to another level: breaking down the digital divide in enterprises.

“There are 615 million knowledge workers in the world but 2.1 billion workers that are not ‘knowledge workers,’” says Jim Patterson, the co-founder and CEO. “It’s interesting that you have all these companies like IBM and even Google going after a relatively small piece of the pie. We’re looking at the other portion.”

Patterson believes that smartphones — becoming ever more ubiquitous — are a great democratizing force. Whereas a shop assistant or barista may not have been connected on a company network in the past, a handset — equipped with the Cotap app — could suddenly change that.

“For the first time, enterprise software will be something usable by all employees. If you work for a large grocery store or coffee chain in customer service, you’ve typically been excluded from company conversation,” Patterson says. “Your closest connection to company conversations happens in the break room, or on a message board.”

That goes two ways, too: those who work at cash registers typically come into the closest contact with customers, and yet there is no way for them to feed information back into an organization.

“In my experience at Yammer and in talking to Yammer’s customers, I know they would benefit greatly in connecting those line workers with knowledge workers. They are in contact with those customers every single day. They have something to add.”

The idea of equipping a huge workforce of line workers with smartphones, or pushing out an app that can be used on their own devicees, sounds a bit like a can of worms.

Patterson believes that this is surmountable, though. He notes that carriers like AT&T already offering enterprises charging plans where usage of specific apps can be charged to a company, as one way around the “bring your own device” trend.

He says that both service providers and enterprises are interested in these kinds of solutions, “the value of bringing people into the fold is so high. Yes, it can be complex to give access to front line workers, but even companies like Yammer and Box are exploring how to do this.”

And on the subject of the handset, when you consider that now companies often require employees to purchase uniforms, it’s not too outlandish to think of how that might potentially extend to mobile handsets, too.

As for paid features that might be coming online with Cotap, two areas that Patterson hones in on are security and push notifications. “Push notifications can be simple reminders, or they can be crisis communications, making sure people get word on something urgent quickly.” He says that Cotap will be offering customers the ability to segment by geolocation or department. “That’s a really powerful thing that companies don’t have the ability to do today.”

Patterson says that right now Cotap is working with around 10 different companies in beta on the new paid services, with the plans to introduce charging sometime before Q2.