Group notifications messages via ESP8266 button and webserver.

I would like to ask for help with a project I have in mind. I would like to have an ESP8266 button ( This one - [login to view URL]). That sends a customized notification message to a group of people on their mobile phones (almost like a whatsapp group) when it is pressed. It must be easy to setup (so that anyone can do it) and connect the button to WiFi too. I'm not sure if a webserver is necessary. The idea behind it is an SOS emergency button that will send notification to group of people once it is pressed. Must work with WiFi. Please let me know what you have in mind on achieving this. I have tried IFTTT and Telegram, but IFTTT does not purge the Telegram group names on their system and I am stuck with many "old" groups that does not exist