Comment by curtpw

There are a number of Chinese generic activity trackers containing the Nordic nrf52832 MCU and a GPS module which are easily hacked and would meet all your needs. Search for "nrf52832 gps bracelet" or "nordic gps bracelet" on Aliexpress, Banggood, ebay etc. For example: https://www.aliexpress.com/item/KINCO-OLED-GPS-Activity-Trac... Components: Nordic nrf52832/ARM Cortex M4 MCU, Kionix KX023 accelerometer, Ublox GPS module, 200mAh battery, 0.96" OLED screen. This can be programmed using the Nordic SDK with Keil, ARM mbed, Sandeep's Arduino Core for nrf5X etc.