Power of Google Talk!
What’s really cool is that many of those computer users have microphones and speakers, and with the right plugin can audio chat with you. This is essentially a free way to make voice calls to anyone in the world with a Gmail account - and it’s built in to every Android out there.
What’s more, if your Android Smartphone has a front-facing camera, you can also use Google Talk to make and receive video calls! You can video call with other Android users, or computer users that have a webcam. This comes in particularly useful during the holidays when friends and family may not be able to come together. Unlike other video chatting solutions, Google Talk should work just fine over 3G, 4G, or WiFi.