U3DXT iOS plugin proximity sensor causing screen to go black?

I'm trying to make use of the iPhone's proximity sensor via U3DXT's iOS SDK Plugin, and I'm running into a few issues.

I seem to be using the API correctly as outlined here, but as I'm trying to use it, it causes my phone screen to go black. (The same way the proximity sensor works as if I would be in a phone call.)

An empty Unity project doesn't produce the screen blacking behavior, so I assume the U3DXT plugin is causing it to black somehow.

Am I missing something in the API that will disable the screen blacking but still let me use the proximity feature? Also, it seems to enable this behavior just by having the plugin in the project, even if I'm not calling Initialize on the Core or calling UIDevice.CurrentDevice().