Vonage (NYSE:VG) is off to the races. Shares of the rocky dot-com telco traded as much as 23% higher today after it introduced its first Vonage Mobile application, which will work with Research In Motion's (NASDAQ:RIMM) BlackBerry and Apple's (NASDAQ:AAPL) iPhone and iPod touch devices.

The free app offers prepaid access to discounted international phone calls. Unlike eBay's (NASDAQ:EBAY) Skype and other Web-based telephony apps, Vonage Mobile isn't restricted to Wi-Fi access. BlackBerry and iPhone users can make their cheap calls over their wireless carrier's network.

This is a huge concession, especially for AT&T (NYSE:T), which has been historically stingy with its iPhone contract exclusivity. Everything from tethering to Google (NASDAQ:GOOG) Voice has hit a brick wall on the iPhone, but now Vonage squeaks through with a way to let people call overseas for a discount ?

Vonage has been here before. The stock opened 44% higher last month, after announcing the approval of its App Store application. The company quickly gave a lot of that gain back, though, when it failed to elaborate on what its app would do.

This morning's news is a surprise. Marked-down international calling may not appeal to many iPhone and BlackBerry owners, but this is just the first of Vonage's mobile applications. Future apps could possibly turn to domestic calling or provide enhanced features for existing Vonage customers.

Vonage still has a way to go before it's profitable on an annual basis, but this formerly moribund dud of an investment now has all the shine of a story stock.   

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Longtime Fool contributor Rick Munarriz is not a Vonage customer and doesn't own shares in any of the stocks in this article. He is also part of the Rule Breakers newsletter research team, seeking out tomorrow's ultimate growth stocks a day early. The Fool has a disclosure policy.