AlertBroadcast

AlertBroadcast is an effective two-way SMS alert system between a controller and a team. Send an SMS broadcast to alert a team in an emergency situation or with time critical information. Broadcasts can be sent simply by sending an SMS from your mobile.

When you need to get a message out quickly to a group of people, you can send it from your mobile phone without the need for a computer or internet connection. A single text message can be sent from your mobile phone to a broadcast number that then causes the text message to be sent out to any number mobile phones. Recipients of the message can also reply back to your message and their reply relayed back to your phone.

This service can be linked to WebSMS for you to send messages to a group of people from your computer using a web browser.
AlertBroadcast User Guide