Yahoo Alerts now offer IM, Email and SMS. All for free. I set it up for my phone for trial and it works pretty cool. Can do any RSS feed. You can choose to have it send you updates one per day or as they happen. Can also limit the number of messages you receive per day to cap things.

One more way to get in touch with people. Will your OPAC SMS when a hold comes in?

http://alerts.yahoo.com/