Bug Watcher allows you to watch issues matching your filters. If you want to precisely define the set of issues to follow, create a filter or select one of you faviourite filters and start watching it.
If an issue that matches the filter you are watching is changed, you'll get notifications according to the notification preferences you set in the issue's project.
Example Use Case
You want to get notified of on changes made to issues with critical or blocker priority affecting a component.
Instead of setting yourself a watcher of all such issues, you can create a filter and start watching it.
As a result, you will get notified upon all issues matching the filter. You will receive emails on the events that are configured in the Notification Scheme of the issue's project with Watchers as recipient.
How to do it?
Got to Filters
Click on Watch next to the Filters you want to watch in Watch column.
The issue events and method of notification (in-app or email) can be set in the Project Watches tab.