The Structure App was designed to be used in conjunction with the Skanect Software and will not allow scanning without it. There are many apps for the Structure Sensor that do not require this though. You can find all the apps on the App Store made for the Structure Sensor by plugging your Structure Sensor into your iOS device and then head to Settings > General > About > Structure Sensor. Once there, you'll find a button that will redirect you to the Apple App Store to show you every app available.
The Calibrator App can be tricky sometimes. Are you using the Structure Sensor with the Wide Vision Lens? If so, please make sure you are calibrating the sensor in the Wide Vison Lens mode. If not, please make sure that you are calibrating with the correct environment. Make sure you have enough light and a complex enough scene for the calibrator to work correctly.
We are in the processes of updating the Calibrator App to support the new iPads, which will include the new iPad Pro 12.9". Please check back soon for this update. In the meantime, you can always skip the warning message that tells you the iPad is unsupported and calibrate normally. You should see a Calibrator App update within the next few weeks.
Please let us know if you are still having difficulty calibrating the device, especially after you've tried the new Calibrator App once it gets released!