http://slideme.org/application/priority-notifications
★★ New notification by keywords
Be notified of text messages that have specific keywords.
Just go to "Menu -> More -> Notification keywords" and add as may keywords as you want.
For example, add the keyword "report" to be notified of any message containing "weekly report".
You can add as many keywords as you want, including whole phrases. If the phrase "annual report" is added, you'll be notified if you receive the message "annual report ready",
but no notification will be played for the message "weekly report".
Priority Notifications lets you be notified of calls and messages that really matter.
Simply select a contact from the contact list to create a priority contact. Any calls or messages coming from priority contacts will generate a priority notification even if your phone is set to be silent.