At least one company that already provides Mac-compatible voice-over-IP services has expressed a desire to work with the iPhone platform after Apple officials disclosed on March 6 that Apple would conditionally support VOIP communications on the iPhone and iPod Touch.

"We are interested and investigating porting our award-winning VOIP service to the iPhone," said Eric Quanstrom, vice president of marketing for SightSpeed. He added that SightSpeed's engineering team is "looking at" the SDK (software development kit).

Quanstrom said his company's product may face a unique challenge, in that SightSpeed's applications focus on video chat, rather than just voice, over IP.

"The biggest high-level challenge of running on an iPhone is actually in the form factor—the camera. Currently, it is on the wrong side of the device—i.e., not the screen side—making two-way video telephony quite hard," Quanstrom said.

"We have solved for many of the other issues, like CPU, in building out our current product suite," he said.

At a question-and-answer session with the media immediately following Apple's SDK announcement for the next software revision of the iPhone, company CEO Steve Jobs said Apple would not block third-party development of VOIP applications for the iPhone and iPod Touch—as long as the apps run over Wi-Fi.

"We'll limit [VOIP applications] over the cellular network," Jobs said, but continued on to say there would be no Apple-imposed limits for VOIP apps that work via Wi-Fi.

But all VOIP products will run up against a common limiting factor, Quanstrom pointed out.

"Bandwidth is the real X factor," Quanstrom said. "We have patented rate control algorithms that do a really good job at pretty low bit rates—think of rates above dial-up and below DSL/cable—but these are still orders of magnitude higher than mobile infrastructure currently allow[s] for [in the United States].