Currently I am working on a project where the app needs to catch the notification for power button click and send a message or something else to a specified address (may be a phone no). I have no idea is there any notification or something to catch the action of power button click. Please help.
No, there's no way of capturing specifically the press of that button.
You get a notification when your app is backgrounded, but it can be backgrounded for other reasons, like the user pressing Home.