SAN FRANCISCO » Get ready to start watching live video of your friends and family doing something fun, boring and even dumb on Facebook.

The world’s largest social network is testing a new feature that will enable its 1.5 billion users to use their smartphones to shoot video so other people can see what they are doing in real time.

Facebook began testing the live video option today among a sliver of its U.S. audience with iPhones. The company didn’t say when everyone with a Facebook account and a smartphone will have an opportunity to broadcast live.

The feature represents Facebook’s latest challenge to online messaging service Twitter, which introduced a live video application called Periscope earlier this year. Another popular app called Meerkat also can be used to share live video.