Vivint: Advanced Home Security
Vivint is a security and connected home service, and the Vivint app for iPad is one of the most advanced offerings around. It's not just a "viewer" with simple lock and unlock controls: The app also lets you adjust your home temperature, view live security camera feeds, arm and disarm the security system and control lighting.
You can also see a history of all connected home events — each time the front door was opened, for example — and you can lock all doors or shut off all lights in one click. The app itself is free, but security systems and video and connected home system pricing varies.