Today TANGO, a free mobile video calling service that works between iPhone 3GS, iPhone 4G, and dozens of Android devices over 3G, 4G, and Wi-Fi announced several developments including iPod touch 4th Gen support, Android version update for Cloud to Device Messaging and more. The app works great on the iPhone 4 and iPod touch, but it has some trouble with the Nexus S' front facing camera. Video quality is good.
Tango supports the fourth-generation iPod touch, iPhone 3GS and 4G, and dozens of Android phones. Tango works with carrier phone and data plans, and on Wi-Fi networks.