The new mod Im working on adds a widget overlay whenever a helmet is equipped.
Video: https://youtu.be/jJDkSva_B5Q
Image: http://i1268.photobucket.com/albums/jj569/Scrivener07/ironoverlay.png
Image: http://i1268.photobucket.com/albums/jj569/Scrivener07/ScreenShot76.png
Image: http://i1268.photobucket.com/albums/jj569/Scrivener07/ScreenShot78.png
Image: http://i1268.photobucket.com/albums/jj569/Scrivener07/ScreenShot79.png
Image: http://i1268.photobucket.com/albums/jj569/Scrivener07/ScreenShot80.png
Image: http://s1268.photobucket.com/user/Scrivener07/media/ScreenShot81.png.html
Image: http://i1268.photobucket.com/albums/jj569/Scrivener07/ScreenShot82.png
In the future I plan to add unique overlays for each vanilla helmet. For modded armors I plan to add support for custom overlays and the ability to associate any helmet with any overlay.
The overlay featured in the video is loosely based on the vanilla iron helmet and is a temporary placeholder.
Let me know if you have questions, feedback, or would like to contribute overlay shapes to the project.