Bt module with mpu inside.

I want to use a mpu9250 on arduino and use a bt ble module for connectivity,some module has integrated microcotroller m0 cortex. Do i need 2 microcontrollers? Is there an advantage? Later device production could just use ble module with intergated m0 and the mpu9250?.

Yeah, without an arduino you are one mcu less on your product. But are you willing to learn to program whatever mcu that is doing the bluetooth function and be able to develop a project with it, and possibly on top of an existing bluetooth code that is also running on that mcu? I assume it is a risk. The reward is only a few thousand products away.

Ok i see better 2 seperate mcu :-)

I did some digging and found that someone has made an arduino core for esp8266. It's a different processor than m0 but there might be someone willing to do this in the near future so you could reduce mcu by one if there is a ready-to-use tool to port your code. My main concern is your time invested learning a new system vs just a couple extra dollars per board. Maybe one day we'll program raspberry pi with arduino IDE :)