BBox Guides is a very simple python tool that we developed for its use in RoboFont. It is quite useful to get the middle of the contours with precision, it works with the current glyph or with the selected contour. There is a clear panel with two buttons on it, by clicking on (+) a bounding box and center local guides appear for a selected contour or the whole current glyph if nothing is selected. Meanwhile, the (-) option remove all the local guides. 

The script is provided as is (without warranties or any kind of support).

You can download it for free at GitHub, please see the link below, or you can install it directly in RoboFont with the Mechanic plugin. It has been so useful for us, we hope you will enjoy it!

BBox Guides   (Updated to RoboFont 3)