Hello matt
You can use the Nimblekit javascript functions to test for wifi or cell data(check the pds docs) and then call the NKBanner function

i do this way qith admod, it only loads the banners if the users has any connection, otherwise i dont call the banner, no need to sunny to implement it on obj c once you can do it on your side. Remember Apple always test the app in airplane mode and wifi off in order to check how it will behave and if it brokes or no frendly alert is displayed to the user about the missing connection the app is not approved.
Hope it helps
Best
