Storing data

Hello guys, I would like to build a fitness tracker similar to UP24, I'm really new with Arduino.
My question is about storage. For example, with UP24 you can store your activity offline, and then later you can synchronize with your phone and download all this data. Which component can I use to accomplish that?

at $25 USD from Amazon, just purchase the UP24.

To do this yourself, you would need a small Arduino board, the sensors, a small LiOn power pack, the battery charger, a low-power Bluetooth module, and a tremendous amount of time to hook-up the hardware and write the software.


Looks like the UP24 is available for about $12.

Note that the Arduino, power supply, sensors and breadboard would not fit on your wrist.