CBS-- Liz Fisher, her 11-year-old nephew and two children wonder what could've happened.

"The timing was perfect. Because I don't always listen in. You know, I'm at work."

Fisher had the home video security app "Presence" open on her desktop at work. And that’s when she heard it.

"I was listening in on my in-house camera. And I heard knocking. And the knocking didn't stop." She wasn't expecting company, so she called her neighbor to see who was at the front door.

“I then heard glass breaking while my friend was walking over. She said she saw some people, and I heard her say, can I help you, then the phone disconnected." Terrified and helpless, the back door out of view-- Fisher could only hear what was happening **in real time**.

The only thing running through her mind? The three innocent children inside. “I was a wreck.” She immediately left work, and drove home.

"There was glass everywhere, the front door, in the kitchen. It was everywhere." Fisher says her neighbor startled the would-be burglars. She hails her a hero.

You can download the Presence app for free.

And you can add as many devices, whether it be phones or tablets.

Now to upgrade the service, you will need to pay for the camera alarm, faster recorders and clearer video streams. You can try it out for $1.99 for a week, the service is usually $50 a year.