I am a beginner when it comes to assembling arduino parts and need some guidance on powering my system. I have an arduino nano, a BLE module, and a sensor switch and need to find the smallest possible way to power it with a battery. What I am trying to accomplish is when the switch is flicked, it sends a signal via BLE to my cell phone. Ideally I would like to power it with something like a watch battery. Any guidance or advice is much appreciated.