Notifications of Task Completion, Comments etc.

Currently, if someone completes a task, you have to go back and go to the contact, search for the task, and see if it's been completed or not. It is time consuming, and not nearly as nice as just getting a notification that a task you assigned has been completed. Similar to this would be notifications when someone comments on a task you assigned. They could tag you in the comment if it's meant for you with a question etc, without having to reassign the task back and forth. Etc.