Yeah, i'm sure someone already did it.
But : 1- if it is sold, then i don't think they'll share their code for free
2- i'd like to design and make my own case (since i have access to several 3d printers)
3- when i searched online with keyword "controll phone with bluetooth request", almost every pages were using "receiver" app while you don't need one with headphones or when in car.
Hence why I come here to see if someone is willing to help 