Need an app for alert by somebody

A

AC Question

Hi Guys!
So I have a friend on the internet who wannts to talk to me sometimes. The problem is that I cannot give her any details about me ...... for safety concerns. I need an app that you know is just small and light and it works like ..... Whenever she wants to talk to me she opens that app presses a button and I get an alert and then I will be online.
Ok this is very confusing but still Thank You for reading :)