BOSTON--AOL is opening up its AIM Phoneline interface to outside developers, hoping to build a compelling product that can compete in the crowded VoIP space with Google, Yahoo!, Skype and others.

Not only is the company creating applications programming interfaces that it is opening up to third-party developers, but it is identifying key developers and working with those companies both to determine what AOL needs to do to become more open and to aid its partner companies in selling products to the AIM Phoneline audience.

“We are trying to be led by the developers--we asked them what APIs they most needed from us,” said Ragui Kamel, senior vice president and general manager of voice services. “What they identified was three areas--call personalization, which includes ringtones and ringback tones, untethered devices and incoming call management.”

On those three interfaces, AOL partnered with leading developers to figure out specifics of their needs and also developed a steering committee to direct the overall effort.

Early on, the devices include a D-link box which connects cordless handsets to the PC-based service via a USB plug-in device, as well as Plantronics headsets.

AOL is partnering with Iotum, a Canadian company, on call management. A sophisticated relevance engine takes into account many different factors in determining how to route calls including the calling number, the called number, the subscriber’s calendar and planned meetings, a pre-determined calling list with priorities and buddy groups set, and presence.

For example, Kamel explained, calls from identified work colleagues may be routed to voice mail until a call comes in from an individual five minutes before a meeting is scheduled with that person. “In that case, the call may go through to my cell phone,” he said.

Customers can order the Iotum service from AOL’s storefront as well.

On ringback tones, AOL has partnered with myNumo, and is selling those services in its store front.

“We think we have the best soft client in the industry,” Kamel said. “Our pricing offer for AIM Phoneline--a free number and free local calling--is also compelling. So the core of the service itself contains huge differentiators, and this set of services extends that differentiation even farther.”

He admits that one of the early tenets of AIM Phoneline--that people would use multiple free numbers for multiple types of contacts--hasn’t proved true. Instead, customers are content to have one free number, which they are giving out to friends and family.