The BoneView app should not need cell service, internet, or wi-fi connection to view your trail camera photos. However, iPhone apps that offer "sharing" features may at times search for options to share, and limit the app function when out of service range, or internet.

In this case, simply put your phone into Airplane mode to negate this. 

Now you should be able to connect BoneView and have your SD Card come "online" to view photos anda videos.

Enable Airplane Mode

From any screen on your iPhone, swipe up from the bottom to reveal Control Center and tap the airplane icon. Doing so will turn off all wireless connections -- Wi-Fi, cellular and Bluetooth -- on your iPhone.