Curb Hero works when a device is offline, BUT for some features to work (ex: creating a new account OR features involving text messaging), you'll need to be online. This can be done by turning on cellular data or connecting to a Wi-Fi network. 

If no Wi-Fi networks are available, you can also turn your mobile phone into a Wi-Fi hotspot. Then you can connect the device running Curb Hero to that wi-fi network. 

Follow the instructions that correspond with your phone's operating system

Setting up a Wi-Fi hotspot for an Android phone:

Setting up a Wi-Fi hotspot for an iOS phone: