Currently, the tag wiki for activity says this:
Activity is the main UI component of the Android System. It represents one particular thing a user can do, one screen of the application.
Really? That's the only thing an activity can refer to?
Shouldn't this tag really be [android-activity]?
Note: Although intent doesn't have a tag wiki, it has the same problem. I could see how you might have these tags on an Android-specific site, but on StackOverflow these tags seem...well, too broad and generic to apply to concepts that are so specific.