I made this over the past few months to help out my Wife's school. They rely on SMS to coordinate teacher absences (finding substitutes, etc). They can't rely on any smart phone app, as the school can't afford to buy everyone one, and then they legally can't require it. The goal was to have a shared, central phone number that all the administrators can access, with notifications when a message is received.
Made with Angular (1.x), Actionhero.js, and Twilio.