Well , yes you are right my topic was a bit loose. But my budget is very limited as a student so i would like to achieve this by using the bluetooth module, even the simplest communication between arduino and bluetooth module is acceptable i mean showing message on phone like serial monitor " Fire alert" . If someone can help me with this would be awesome. I know that by using a GSM module would be more useful but as i said i can't afford to buy it. Thank you in advance.