If you send encrypted text messages from your phone, there's a decent chance you use Signal. Since the app made headlines in 2015 by offering encryption between Android and iPhone, it's grown in popularity, to the point that it's now one of the preferred ways to tip The New York Times on a story.
As of today, Signal will do video calls as well.
Mind you, Signal creator Open Whisper Studios is calling the feature a beta for now, which suggests it might still have its share of bugs.
And if you're using an iPhone, there's one thing you may want to do for security's sake as well: since the app uses Apple's CallKit on iOS 10 to let you answer calls from the lock screen, it will send a record of who you called, and how long you spoke, to Apple's iCloud servers.
The creators aren't trying to hide that, by the way -- it's plainly disclosed in their blog post.
Signal's creators also say the update should improve standard voice calls as well, since the company's using an "entirely new calling infrastructure" for both. If you code, you can check out the details in their GitHub repos.
You'll have to opt-in if you want to try video calls for yourself: Go to Signal Settings > Advanced > Video calling beta to enable the feature, and Settings > Advanced > Use CallKit if you want to disable the CallKit features on an iPhone.