Hi,
For your Case, I think we can use NRF51 Microcontroller from Nordic. It's already contain Both Bluetooth and ARM Cortex M0, And we just need to add some voltage regulator, battery charger circuit if you want, and Of course Accelerometer itself. It's already support Arduino Environtment, So it will be easier to program it. But if you are not confident with having Bluetooth and Microcontroller combined in one SoC, we can use separate ARM Cortex M0 device, it can be STM32F0, or another MCU, Just discuss it.
I have managed several similar project before, and I know some of its related PCB design Issue, like Antenna, Power, charging, etc. I will use Eagle to deisgn this PCB, and I think 2 layer is enough. I just need to know your dimension constraints.
I have became PCB designer since 2012 and has done lot of project for various application, from hobbyst to Military based. My background is electronic engineering, so, I know how to analyze circuit refering to it's design guide.
Let me know your response about my proposal. If you Ok with this then we can start this project soon. It's fairly simple project in PCB design. I will provide you manufacturer file and BOM, so you can order it to PCB manufacturer. I will recommend Chinese manufacturer for this.
Best Regards,
Rijal