Having to repeatedly reload our Corona project to see if we'd coded our UI positions, sizes and angles correctly was a bit of a pain. So we made a helper to measure and call out these values in Corona simulator using the mouse cursor. Sharing it as a plugin in case anyone else finds it helpful.
Require the plugin while developing. Hit 'c' on the keyboard and move the mouse around to call out positions (absolute and relative to screen size). Click and drag on the screen with 'c' pressed to get the dimensions and the diagonal angle of the resulting rectangle.
Note: (a) This uses Corona's 'mouse' events. All the gotchas of mouse events apply. (b) This is meant as a Simulator helper. The plugin will not activate on device builds.