Need help send alert or a text with arduino with smartphone via bluetooth

Hi everyone, im a newbie today i need help with this project.
i have a arduino mega 2560 + module mq3+ module pulse sensor and hc-05 , 1 app android to see data from 2 sensor which i had make that app from android studio . The issuse here is i have recieve the data from 2 sensor to my android app but i dont know how to send alert or send a auto message that when mq3 turn high( it mean >500) then it will send message to another smartphone via bluetooth .

Is it need to write something in android studio or need more any module to do that job .Please help!!!