This is a very interesting project and much familiar to us as we have worked on blue tooth and other communication protocols like SPI, I2C, UART. We are currently working on ARM CORTEX M3 which is the main part in this project, as the size of the device you want is small.
For 3D printing , we have our team of 3D designers & animators along with 3d Printer,so that we can provide you the complete solution.
First for weight scale measurement we will use Digital Scale Strain Gauge Weight Sensor and the data will be send by interfacing Bluetooth module to the device.
For OLED display, are you talking about Samsung OLED displays, which is flexible. But the interfacing technique is I2C communication mode, so we have interfaced LCD using I2c protocol , hence we can easily interface OLED also.
For Data Recording and Access, we will use EEPROM for read and write operations, interfacing will be done using I2C protocol.
For rechargeable battery, we will use Li-Ion battery and charging type will be USB charging.
Hardware cost will be provided only after complete requirement list.
HARDWARE REQUIREMENTS :
1. STM32 Development Kit
2. Bluetooth Module- nrf1822
3. OLED display
4. EEPROM
5. Li-ion Battery