Send predefined sms/text message to group with a shortcut I would like to install a "panic button" on my phone's home screen or lock screen that would send a predefined sms/text message to a selected group of people.

I am NOT looking for a group sms app where you first need to wait for the app to start up, then need to select the group, then type a message, then handle various menus/screens/popups/confirmations to send it.

It should be quick and easy (with hopefully only one or two clicks or swipes) to send the predefined message to a group in a life threatening situation.  It should enable me to notify e.g. my neighbours, police, security, family, etc. immediately and simultaneously in a case of emergency.

Is anyone aware of such an app or any way to customized an existing app/feature to get this type of behaviour?
Check out WithU app 

WithU connects you with your family and friends in any problem. WithU is an emergency App that, at the click of the Start button begins sending out alert messages in every 2 minutes to your contacts that you saved into the app as the receivers or guardians.
Enter Contacts Numbers of People whom you wanna inform whenever you are in Trouble. If you feel Unsafe, Distress, just press Green Start Button, It will send SMS (With your location and Time) to the Saved Numbers.
The message says "I am in Problem. Please help me. My Location is (Your Current Location)". Even if you have not Internet Connectivity , it send SMS to your contacts with message "I am in Problem. Please help me".

You can place the button on your homescreen.