Create notification when bluetooth data is received: Hard to code? [on hold]

I am currently working on an arduino project that connects to my phone using a bluetooth module.

On the arduino I have various diagnostic sensors hooked up to it. When the sensors "sense an error," I would like to receive a notification on my phone.

I'm guessing this would require me to program an app that runs in the background listening for data coming across the bluetooth connection. Then when it receives the data, sends a notification to the phone.

How hard would this be for me, a beginner, to program? I have programmed in several other languages (html, visual basic, and python), so I understand basic coding concepts.