Twitter has announced a new service called Vine, through which you can share short looping videos on Twitter. The videos can be up to 6 seconds long with sound and loop automatically on the website like an animated GIF.
To capture one of these videos, you will need to download the Vine application, which currently is only available for the iPhone and the iPod touch. The app is very similar to the Instagram app, but instead of square images you see square video clips on your timeline.
You can download Vine application for your iPhone or iPod touch from here: https://itunes.apple.com/app/vine-make-a-scene/id592447445
Hopefully, the Vine app will be released on other platforms shortly.