Hey there. I recently made a mobile calorie consumption tracker for my non-motorized skateboard. It has an accelerometer (MPU6050), a bluetooth module (HC-05), and a magnetic switch. The magnetic switch is positioned near the wheel and I mounted a magnet on the wheel. So each magnet pass is 1 RPM. Accelerometer is there to measure hill climb which affects the power exerted to climb hills or rocky terrain. Writing an algorithm to calculate my calorie expenditure while skating. I know its not gonna be very precise, but I wanted to see where the project might head towards. The problem is however, when everything is put together, the system is acting erratically. The bluetooth turns on and off, and it finally broke after around 2 hours on battery testing. The whole thing is connected to a 7.4V 850 mAh li-po. The li-po is dead too! 
Here are some pictures of the setup. Once I realize what is causing the problem, I will move this project on a PCB for reducing its size.
