Anybody ever hear of email?
Don't think I saw a single mention of email in this thread. You know that email address you have? That everybody already knows? Setup up your smartphone email to use IMAP IDLE to the server instead of ancient POP3. Tell your phone to "ding" when you get an email. It is instantaneous, no waiting for the email client to poll every XX minutes.
Problem solved, same thing as text messaging using what you already have, and an address your friends already know. No need for an SMS app with a phone number, handle, or ID your friends will need to learn.