Looking for a very cheap development board with Bluetooth (BLE) and accelerometer built in.

I have an assignment where I need to process data from an accelerometer attached to an object. I am left to source the sensor and dev board myself. Does anyone know of the cheapest option that can be run on a battery? Something with a recharging system built in would be ideal and the smaller the unit the better. I am currently using the Arduino ide to program other larger dev boards but not necessarily married to that dev environment if there is a better option.

Thanks in advance!
Always learning......