As you already know FcaeTime on iPhone 4 which apple called they invented video call to share live moments and works only on WiFi between iPhone 4. Well, here is the time to show Apple once again how limited they are. An amazing app called Knocking live video arrived for multiple Mobile platform. You can use Knocking Live Video for sharing live video using Phone camera as a web-cam, between cross mobile platform and it doesn't required WiFi. You can use on both WiFi and 3G. Just sign up and create your own account as a Knocker.
To get a clear idea how it works watch the video below knocking to iPhone 4 using Google Nexus One.
To get Knocking Live Video on your Android Smartphone just browse market.