FWIW, I believe in the newer versions of the firmware and mobile apps, you can provision and configure the APs directly from your phone. The need for a controller was a major limitation in recommending the gear to other people, but the new iOS/Android apps can basically manage a small fleet of APs with nothing else than a few clicks in an app.

Of course, this requires a recent enough firmware version on the AP itself to support that feature, which, when I first tried it, I conveniently did not have, meaning I had to install the controller to upgrade everything anyway...

My lesson for that one is, uh, don't buy the older gear from resellers. Buy the new models from Unifi or Amazon directly.