Enable watchers/owners for categories within products Merged

I work for an accounting software company. Our accounting products are complex so there are several functional areas managed by several different product managers within each product. 

I'm creating an ideas portal where AccountRight (our major product) has 8 subcategories. I want to be able assign a product manager to the category they work on within AccountRight. The product manager doesn't want to see the ideas coming in for the other 7 categories, they only want to be notified when ideas come in for the category they own. 

I want an option where the product manager be assigned or be a "watcher/owner" of the category they own within the product.