Cloud telephony platform Twilio announced Tuesday that it has secured a $12 million Series B round of funding led by Bessemer Venture Partners, with participation from Union Square Ventures, Dave McClure’s 500 Startups and angel investors. The new funding will be used to fuel product development and to make new hires in sales, marketing and engineering.

Ty Wang, former senior director of the business communications unit at Oracle, will now serve as vice president of business development at Twilio. Bessemer Venture partner Byron Deeter will be joining Twilio’s board of directors.

Nearly a year ago, at the end of December 2009, Twilio closed its $3.69 million Series A, following a $600,000 seed stage.

Around the time of that Series A round, Twilio was serving about 4,000 developers, a number it says has multiplied to 20,000. And those developers are paying less for the service than ever before. In September, Twilio announced price reductions for customers that would result in an average of 29% in savings, made possible by “new levels of scale.”

Developers can use Twilio’s communications platform to build a vast range of different telephony applications. Customers like Salesforce, Cheetos and Tumblr that tap into the Twilio API can mold the service to their own liking, building interesting and powerful phone tools.

OpenVBX, a Web-based open source phone system for business (pictured), is just one example of what a Twilio-powered application is capable of. Another Twilio-powered application just launched two weeks ago called TextSlide, which is being described as ChatRoulette for text messaging.