Vivint does NOT require the internet. The system will still work even without an internet connection. Their system works through the cell towers. Inside of the panel is a cell chip that is used to notify Vivint’s monitoring station if the alarm is tripped.
The sensors connect to the panel through a radio frequency and the smart home items such as a door lock, thermostat, and garage door opener work through z-wave. Z-wave is a wireless technology that allows for items to talk to each other. It is kind of like bluetooth but for smart home items. This means that from your phone, you can still control the alarm and your smart devices even without the internet.
The only feature that will not work without internet is streaming live video from the cameras to your smartphone. The cameras will still record and can still be seen from the panel even without internet. So if you are on a vacation and your internet goes down, you will not be able to see what is happening in real time on your phone. However, you can see any video recordings on the panel itself once you return from your trip.
Their ability to record video to the panel without wifi is a unique feature to Vivint. If you are interested in learning more about their service and what they offer, you can check out my Everything you need to know about Vivint. I also have a separate article discussing their pricing. Vivint is a great fit for people looking for both security, cameras, and ease of use. I would highly recommend them.