Initially, I roughly design the device to meet the following points:

1. Slim and small
2. Cellular connectivity
3. GNSS -based location tracking
4. Low-cost
5. Battery-powered and Rechargeable

Working on the schematics, I was able to achieves those points and choses the following components and design:

1. Credit card sized board
2. SIMCom A7670 for LTE CAT-1 Connectivity
3. Quectel L76L-M33 GNSS Module
4. ESP32-S3 as the main MCU, for low-cost and possibility of adding bluetooth tracking

Once the initial schematic is done, my friend Theo, was able to help me on layouting and tracing the initial design in KiCAD. The following was the initial design of the device.