Since I won a LightBlue Bean in my other project I am thinking of making it to use in this project. I will use the Bean as the main controller. The only additions that I need are display, RTC and a PPG sensor. I can use the on board accelerometer to develop a pedometer which can count steps and from that determine the calories burnt. This will be a cool low power fitness band with built in BLE connectivity. Hence connecting it with smartphones will be a breeze.