Keywords aren't limited to text anymore, not if San Jose, Calif.-based startup Pudding has its way. The company has developed technology that allows ads to be served based on what people say when they use VOIP.

Pudding works by serving up ads based on thousands of keywords logged into its system. For example, a conversation about dinner plans with a friend over VOIP could lead to an ad for a local eatery.

While the technology may seem intrusive to some, it could be a savior for the VOIP industry, which hasn't been able to figure out how to monetize free phone calls over the web.

"Think of us as the Google AdSense of voice," Ariel Maislos, CEO of Pudding, told CNN. "Free calls are going to have to happen. We're providing a platform for the providers to monetize their services."