A couple of weeks ago we covered Rebtel and their improvement to their iPhone application. Little did we know that last week they came out officially with a whole lot more than just free calls between iPhone users, as we titled the post. Rebtel has announced some cool new technologies to their application as well as making the free calls platform independent.

The technology Rebtel came out with is KeepTalking. The solution allows users on a WiFi/3G connection to switch to a local call if the connection quality begins to deteriorate. The transfer is seamless, according to the company and all you need to do is click on the KeepTalking button on your smartphone to transfer the call to a local number for better quality.

The market for telephony services is huge. According to Rebtel, it’s twice that of all TV operators and three times more than all internet related revenues. Voice calls generated some $628 billion in revenue for operators last year, which is two thirds of all revenue and accounts for half of all the profits for the companies. Furthermore, if we add mobile messaging, which generated 19% of all revenues and 45% of profits, we’re very close to understanding how operators make their money.

So how big is the VoIP market currently? By 2016 it is expected to reach $36 billion. That’s little over 5% of all voice generated revenue operators create. This means there are still huge possibilities in growing the whole industry. Towards the end of 2011, a study by Visiongain expects the amount of VoIP subscribers to grow to 70 million users.

Below is a quick video showing the new app in action.