Zenkit

Want to receive a notification any time a change is made to a particular item? Maybe you only want notifications when items are moved to "Done". Well, now you can set this up in a couple of clicks!
To subscribe to a single item, open the "..." menu at the top of the item, or the quick edit menu on the item, then select "Subscribe" from the drop-down list.
 

To subscribe to a filter, set up a saved filter, scroll down, and toggle "Subscribe". To reaccess this after the filter has been created, open the filter menu, select your saved filter and click "Edit" next to the filter's name.