What happens if I am out of range of a data or WiFi signal?

So long as the app is previously synchronised with your latest form version and data sources, then the app has everything it needs to open a form and save all entered data.

When a form is complete and the upload button has been clicked then so long as the app is active in the foreground then the app should synchronise with the cloud. A periodic check to see if the phone is within a data signal and then making sure the app is running just like any other app, would ensure a successful synchronisation.