For all At & t Iphone users, we spent days looking for an application can save some money by sending text messages or make calls, and so I’m pretty sure everybody who has an Iphone or Ipod Touch has Skype SPA installed, or perhaps SMS, BING SMS, etc..
The truth is that so far the most productive in my view has been SKIP, simply because we can chat, send messages and even call other users with an Iphone or a PC via Skype. But I also accept that the Skype interface is a bit heavy to hang up the iPhone coming in some occasions

As an alternative to the many applications come free dial Ping! An interesting messaging service free for iPhone to iPhone! so users of these phones can chat totally free of charge as if it were to SMS throughout the world. To do this we need an Internet connection, whatever, like 3G, EDGE, WiFi, etc., Since the service relies on the Internet to send all messages, hence has no cost.
All we have to do is: Once downloaded the application, we create an account which would become our PING ID, the same that we will be able to send messages as a Yahoo or MSN. The interesting thing is that this service is grstuito (of course only be paid for the application), just enough to have an Internet connection, whatever, like 3G, EDGE, WiFi, etc., Since the service relies on the Internet for send all messages, kind of like a chat but using short text messages.
And we can download from the Apple Store at only $ 0.99 USD
