T-Mobile

T-Mobile USA's Bobsled, an Internet-based calling and messaging service, has become the little engine that could.

In a little more than a year, Bobsled has exceeded 1 million users. That's an impressive benchmark considering the service gets practically no marketing support and has little consumer awareness.

"The popularity and continued growth of the Bobsled service is testament to consumers' desire for simple ways to stay connected with friends and family," said Brad Duea, senior vice president of T-Mobile.

Bobsled was one of the side projects T-Mobile launched last year in the middle of its planned takeover by AT&T. The service was a bit counter-intuitive for those who follow the industry. Because Bobsled runs off the Internet, it could circumvent traditional voice minutes and text messages, something T-Mobile depends on for much of its revenue. That means any data plan or Wi-Fi connection would suffice.

The free service, while not something a traditional telecommunications company would likely embrace, falls in line with T-Mobile's role as the industry's disruptive force. The carrier is the underdog willing to experiment with different services in a bid to claw market share away from its bigger rivals such as AT&T and Verizon Wireless.

T-Mobile has previously said it was fine with the tradeoff of decreased voice minutes and text messages, noting that it would gain it back via an increased number of users attached to its service. But it may end up being more of a pain to its rivals. The carrier said that of its users, 95 percent are not T-Mobile wireless subscribers.

Bobsled can run on any phone on any carrier, including the iPhone, something T-Mobile has been desperate to associate itself with. The company clearly notes in each of its Bobsled announcements that beyond Android phones and tablets, the service works with iOS as well. Since April 2011, 10 million calls have been made on the service, with 80 percent originating from an international number.

On the messaging side, 90 percent of the messages are sent domestically.

T-Mobile previously said it had hoped the service would get large enough to start delivering ads and providing additional services.