The CamRanger mini is a stand-alone device that connects to select Canon or Nikon DLSR cameras with a USB cable. It creates its own WiFi network that your smartphone, tablet, or computer can then connect to.
The free CamRanger app then enables control of the camera. There is no need for an existing Internet connection or other equipment.
The built-in lithium ion battery lasts about 3-4 hours. The battery is charged through the USB micro port. The WiFi range is over 120m, though the range depends greatly on the exact location and scenario.