I am wondering if when you create a Python add-in, you can have it only contain an extension (no menus or tools), so that when the extension is on, there is an event-triggered process always running in the background? My objective is to update text elements on the layout whenever the user selects a new feature in a certain layer, and I don't think this could be accomplished with a tool, because you would have to run the tool each time you selected a new feature. I have created an extension and written some code for it, but when I install it, it gives the warning that there are no UI components to the extension, and it does not appear in the list of extensions in ArcMap. Hopefully this makes sense.
Thanks in advance for any help you can give,