If you’ve ever been a blackberry user, you’ll get the gist of this immediately, think Blackberry Messenger but for the iPhone.
Ping! is a instant messaging client for the iPhone that looks and feels like the built in iPhone SMS client. It aims to provide free iPhone to iPhone (and iPod touch on wifi) messaging.
Once you’ve download the (currently free) app and selected a username, you can invite/find friends and family you know own an iPhone or iPod touch, and you’re ready to go.
Once you’ve started a conversation, the application works just like the SMS client except it’s free, instant and works internationally at no extra cost (aside from your international roaming costs that is). Whenever you receive a message you’ll receive a push notification and you can respond just as you would with SMS.
The UI is clean and simple, there are a few odd bugs here and there but it is the very first release so expect them to be cleared up soon.