With the numbers of people using messaging apps already huge and still growing, many developers are looking for easy ways to build the functionality into their own apps.

One startup, called Layer, has built the infrastructure and front-end user interface tools developers need to do just that.

San Francisco-based Layer offers the infrastructure as a hosted service, and the service went into general availability today.

The front-end tool kit is called Atlas (also generally available as of today). Atlas provides a set of open-source tools that allows developers to add messaging “as well-designed as iMessage” to any iOS or Android app, the company says.

For the past year, Layer has been working with a limited set of customers. “Due to the technical complexity of the network we’ve built, we wanted to ensure the system was extremely fast and highly reliable, capable of powering messaging in mobile apps all over the world,” Layer’s CEO Ron Palmeri said.

Despite the self-imposed limit, Palmeri said demand has been great. The company says 1,500 customers are now developing using Layer, and that it received more than 10,000 requests for access to the platform during the past year or so.

Palmeri was the man behind Grand Central, an IP voice app that was sold to Google and eventually became the tech behind Google Voice.

The Pop and Imoji apps are examples of live apps using messaging from Layer.

To date, Layer has received $14.5 million in venture capital from Jerry Yang’s AME Cloud Ventures, Bloomberg Beta, Homebrew, Data Collective, and others. The company now has 30 employees, 25 of which are engineers.

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