Can I run the app without the device being plugged in?

Sure, as long as the device has battery power remaining or you are using a supplemental power source like an external battery.

If you are planning on going without power for more than a few hours, you will need to consider how you can conserve or extend battery life. We've incorporated several power management features in our Plus and Enterprise versions that can help, including the ability to dim automatically while idle on the homepage or to allow auto-lock of the screen (which requires access to the physical power button to wake).

For projects with shorter 'power out' periods, like a simple overnight period, we've had clients who have successfully used Night Mode, either alone or in combination with an external battery pack to help sustain battery power until the power is turned back on. As there are several variables in play, including the length of the time without power, screen brightness settings, WiFi and/or 3G usage, and the version of iPad you are using, generally some testing is required to determine whether these will work for your project.