Google have released Duo, a simple video calling app for Android and iPhone. The FaceTime rival is now available for download and free to use. The aim is to make video calling as easy and reliable as possible, Google Duo stops you worrying about whether your call will connect, or if your friend is using the same type of device as you are. The entire user interface is designed to be intuitive and simple to use, a video call can be initiated with just a single tap. Duo works well even on slower networks, and will switch between Wi-Fi and cellular data automatically without losing your call. Another cool feature is “Knock Knock” which lets you see live video of your caller before you answer.