The inexorable march toward data-based phone calls proceeds with steady, clomping footsteps. Why pay for a separate voice plan, estimating the amount of time you might want to talk that month, when you're already paying for a set amount of data? Apps from Skype, as well as video apps like the iPhone's FaceTime  and Android's Fring, use data, and Vonage looks to be next .
Vonage, of the annoying commercials, is a pioneer in VoIP (voice over IP) technology. Personally, I'm surprised it took them so long to get into the mobile VoIP game. But the company's new mobile app, available for Apple 's iOS devices (iPhone, iPod Touch, and iPad) and Android devices such as the Droid, looks like a promising first step.
The Vonage app works closely with Facebook : You log into Facebook, and Vonage automatically populates your contacts list with your friends. You can only call other people that have also installed the app, but you can instant message with anybody.
It's an especially good deal for those of us with Wi-Fi-only devices such as the iPod Touch and some versions of the iPad. The app essentially turns those devices into free phones, albeit with a limited range and use. But still, it's a nice idea, and the integration with Facebook is welcome, if a little restrictive.
The Vonage app is available for free in both the App Store  and the Android Market.
Dan Nosowitz, the author of this post, can be followed  on Twitter, corresponded with  via email, and stalked in San Francisco Brooklyn (no link for that one--you'll have to do the legwork yourself).