Voxer is making its entrance into the business world with a set of new high-end features for its walkie-talkie style, push-to-talk service.

Voxer Pro and Voxer Pro For Business run on Android and iOS devices just as with the standard service. If unfamiliar, the Voxer service is an app for sending voice and text messages. Download the app, import your contacts and then start sending messages. It’s somewhat ideal for this asynchronous world. The messages can be sent without having to make a call in order to talk on the phone. That may seem impersonal but it is a bit like keeping a correspondence with someone.

The standard app is free. Voxer Pro is $ 2.99 per month or $ 29.99 per year. New features include an interrupt mode and, the one I love, extreme notifications, which come in as loud repetitive alerts. Voxer Pro Business costs $ 4.95 per month per user until October 1 when the price will increase to $ 9.95 per month per user.

Voxer Pro Business  also has what the company calls Voxer Pro Manager, a desktop business communications system that provides administration control and visibility into the company’s network with a real-time map with geo-tagged location to help manage employees.

The Voxer service has amassed millions of users since its launch in 2011. It always seemed to me a bit simple and I wondered how much it would last. But how wrong I was. Apparently it has been the intent all along to offer Voxer as a business service. And what a smart move it is proving to be. In combing through all of its data, Voxer has found thousands of people who are using Voxer for their work. As Liz Gannes wrote today, about 21,000 Mary Kay Cosmetics sales people use the service. That shows how deeply voice messaging can spread into society.

It reminds me of my interview yesterday with Carlin Wiegman, the co-founder of Biba, a conferencing and messaging service. Wiegman sold his company, CubeTree, to SuccessFactors in 2010. He explained that the enterprise social networking technology developed by CubeTree, Yammer and the others in the market did very well but they all capped at tens of millions of users. He attributed that to the lack of adoption outside of the young worker set accustomed to using activity streams to message each other. But voice and text messaging has a much deeper market reach. Texting reaches hundreds of millions of people. Messaging systems have that same potential.

Just look at Voxer. In a few years it has amassed tens of millions of users. Social networking services inside the business world have taken years to reach anything near that kind of user base.

And so Voxer surfaces an interesting possibility. Is messaging the killer social enterprise app? If so, then you can expect a swarm of competitors attack this space.

But the big target for Voxer is Nextel, which has amassed a fortune with its walkie-talkie-style service. Nextel represents the old-school heavyweight enterprise systems that integrate proprietary devices for communications. Voxer is replacing the hardware with software, available across any device.

Then there are the Microsoft Lyncs and Skypes of the world, along with Cisco and the tens of thousands of apps from the Twilio ecosystem. There are even the likes of services such as Twello, the Twitter-based voice messaging platform.

It’s a crowded field but Voxer looks like it’s off to a smart start, using messaging for those everyday uses of the modern workday.