On my Bitbucket dasboard I can see all Pull Requests I am involved in als creator or reviewer.
I'd like to see also the pull request that I only watch.
As far as I know, I get e-mails when there are changes to those watched pull requests. I get a lot of e-mails and I filter bitbucket mails and rarely read them.
My reason to watch those pull requests is solely to know when their build was successful.
As a workaround I make myself reviewer. But this causes problems with our merge policy that all reviewers have to agree. (I don't want to review the code and don't want to pretend I did by marking it green).