Facebook's $19 billion acquisition of WhatsApp earlier this week was the latest sign that social messaging is having a moment. Indeed, there has been continual advancement in the space lately, with new startups popping up regularly to push apps you didn’t realize you wanted.

"It is clear that one of the biggest growth areas in social is in messaging," says Toby Daniels, founder and executive director of Social Media Week. "When you combine messaging with another explosive phenomenon such as mobile video, you have the beginnings of what we regard as the next trend in how we communicate."

Founded last year, Samba, the Israel-based maker of a new app that records people's reactions to video messages they receive, is hoping to cash in on that trend. Named one of the startups to watch at Social Media Week in New York City, the company is attempting to carve out an audience somewhere in between the legions of selfie-sharing Snapchatters and double-tapping Instagram addicts.

"We want to win the world in this category. It's not going to replace anything," says Samba CEO and co-founder Barak Hachamov. "There is always room or a gap between services to give you an opportunity to bring something new that mimics human behavior."

So how does the Samba app, which launched Thursday, work? You record a video (up to 15 seconds in length), and select a recipient from your contact list. When the recipient views the video message, his reaction is immediately recorded and sent back to you. Unlike on Snapchat, the video messages do not disappear after being viewed.

"Why send something to someone unless you can get a reaction?" Hachamov says.

For now, Samba only lets you send videos to one person at a time. The iOS-only app is currently free; Hachamov says it will remain that way and that the company is looking into other revenue options. 

Here is a video of Samba in use: