Implementing VoIP is a popular business model these days, and the founder of Google Voice is at it again.

Google Voice hasn’t always been Google Voice. In fact, it wasn’t even always Google’s. One half of the brains behind the original project recently tweeted that his latest venture, Firespotter Labs, is working on an exciting new VoIP project. Who knows, maybe it will become as popular as Google Voice.

GrandCentral was the original name of what has become Google Voice. Chris Walker co-founded the product in 2006. One short year later, Google saw the potential in such a system and bought the product in 2007 for over $50 million. Two years after that in 2009, Google relaunched GrandCentral as Google Voice, with some additional features. The technical name for a product like Google Voice is a phone management service.

The key to the product is that you’re given a phone number when you sign up for a Google Voice account, which can then forward phone calls, voicemails, and text messages that the Google Voice number receives to different phone number (or even multiple phone numbers). So, you can get calls to a home phone number intercepted by Google Voice, and then forwarded by the product to, let’s say, your cell phone.

The call-forwarding feature can be highly specified so that only certain phone numbers are forwarded through and specifically where they go. For example, you could forward calls from your boss to your cell phone but calls from your dentist to your home phone only.

Gmail got Google Voice integration so users could make phone calls directly from their browser window. This implementation is done using VoIP. Using VoIP to make phone calls is much cheaper than using traditional technologies, which is why many companies are so quick to try to implement it (one of the most popular and visible companies is Vonage, for example).

Other cool features of Google Voice include voicemail transcription (where the transcript can then be sent to your email and cell phone via text), texting online, and listening to voicemail online. The product also has competitive long distance rates for making international phone calls.

Walker left the Google Voice in 2010 to found Firespotter Labs, but he didn’t go far. Google Ventures offers office space and keeps talent around as “entrepreneurs in residence.” Specifically, Firespotter Labs isn’t just a company focused around VoIP – the company proclaims itself as an incubator for start ups. GrandCentral originally came from another startup incubator called Minor Ventures.

The crux of Firespotter Labs business model is that the company will build initial products that it thinks has future potential. Then if the product really proves to have that potential, the company will hire a new team to go get outside funding for the project. The idea was foreign to me, but apparently it is an up-and-coming business model in this fast paced, entrepreneurial, and global marketplace.

Firespotter Labs has a proven track record as well. The company has launched Nosh (a food photo-sharing app), NoshList (a waitlisting application for restaurants), and Jotly (a spoof app that let’s users rate literally everything). And even Google Voice showed promise as a VoIP app in the Android store but was never actually released.

One TechCrunch reporter pointed out how integrating a VoIP feature into NoshList would actually make the app that much more valuable. Say a restaurant doesn’t want to implement an interface to accept reservations via NoshList. The app could find the phone number for the restaurant and facilitate a call directly from the app to the restaurant to make a reservation.

Regardless of what Firespotter Labs and Chris Walker do with VoIP in the future, the technology is incredibly popular and is gaining ground. We recently highlighted Skype, which uses VoIP to facilitate calls between users and users to non-Skype users. Click through to read our Skype case study and learn more about how VoIP works.