Its been suggested before, but Mahz hasn't said yes or no. But when he does revamp subscription system, its not unlikely he'll add something.

look here for prior threads:
A number on the Subs button to show how many of your subscribed threads have new [url=http://www.roleplayerguild.com/topics/7501/posts/ooc]activity.[/url]

Email Notifications for the subscriptions [url=http://www.roleplayerguild.com/topics/722/posts/ooc]system.[/url]

Cellphone notifications/[url=http://www.roleplayerguild.com/topics/2159/posts/ooc]app.[/url]

RSS [url=http://www.roleplayerguild.com/topics/14658/posts/ooc]Feeds.[/url]

These four are from the comprehensive list of requested features.