Does the app use Bluetooth or Wi-Fi? Can I use it off grid?

Shutter uses Wi-Fi Direct to provide camera controls. This means the network is generated by the camera itself, you don’t need to stay on your home or office network. You can take Shutter to the most remote location and it will still work.

With the Canon and newer Sony cameras, you can use Bluetooth to initialize the Wi-Fi connection eliminating the need to navigate camera or iOS menus. All other Sony cameras use NFC to achieve similarly easy connection process.