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I am a Google Voice user, but I have not used it much for outbound VoIP calling. My friends often ask me why I use it since its primary benefit to many users is low-cost long distance calling. I use the system primarily to route inbound calls to different phones that have better coverage or battery life than whatever handset I am carrying. Since AT&T coverage is spotty at my home, and I don’t like to carry my phone around the house, I try to route inbound calls to my landline so I can hear the ring on all the extensions.

Google Voice also lets me send SMS messages seamlessly continuing a conversation thread between my home PC and my cell phone when I go mobile. I don’t use the service to make outbound calls mainly because I don’t have challenges with my long distance bill as most of those calls are domestic and can be done within my cell plan as free mobile-to-mobile minutes.

Occasionally, I will forget to deactivate a phone number I no longer wish to route calls to when I am on the road. Since there has been no Google Voice app available for my iPhone, I put a browser shortcut on my home screen so I could quickly access the Google Voice website and change the settings when I am away from my PC. Today when I did that, I was surprised and delighted to find that my experience had completely changed.

Google Voice is now a web app. A web app differs from a website because it creates a unique experience for every session and visitor. When I interacted with the web page, Google Voice provide my device with a newly coded page which told my phone to update the icon on the home screen shortcut from a picture of the Google Voice web page to a neat, streamlined Google Voice icon.

Google developers used HTML5 to support  outbound voice calling and avoided the Apple App Store approval process, which previously led to a rejection of the downloadable version of the application. A phone number in your Google contact list that is accessed through the new web app - or entered in the web app's dialer - will connect through the standard iPhone calling function.

The call will actually use the AT&T voice network to connect the call but route through Google Voice and appear to the person you are calling as if the call came from you Google Voice phone number, hopefully avoiding some pesky international long distance charges you might incur. Oddly, though, to do that routing through Google Voice, the phone appears to dial a number with a totally different area code than the one you are actually calling.

The biggest challenge to using Google Voice on your iPhone will be the segregation of contacts between Google Voice and the native iPhone Contacts application. If you have not synced with Google contacts before, that will take some effort, especially to move the local contacts from your device to the Google Voice service. Wired has done a nice job of explaining the various alternatives to accomplish this migration or sync. You will also need a Google Voice account on top of your AT&T voice plan to place and receive calls.

One of my favorite benefits of using Google Voice is that it lets you replace your caller ID with your Google Voice number. The Google Voice web app now lets me make an outbound call from my iPhone but display my Google Voice number if I choose in the web app’s settings. I like to use the call screening features of Google Voice, which means I also like to manage what number displays when I dial different contacts.

For professional contacts, I may choose to display my Google Voice number, making it more likely callers will return the call to that number. I can then have the Google Voice service “announce” who the inbound caller is the next time they call allowing me to screen callers coming from corporate switchboards or numbers with blocked caller IDs.

What makes all of this possible now, even though Apple previously rejected the Google Voice app as a download from the App Store? The iPhone, like the Palm Pre, Palm Pixi and Google Android devices all use a browser that shares rendering technology based on Webkit, an open source web browsing engine that is one of the first on mobile phones to support this new update to HTML. Some of these devices may require an update to the device’s firmware in order to have the full Google Voice experience.