Kids OK, with an adult
DIY project. Children must build this only with an adult (16+ years) beside them at all times. Not suitable for children under 8 years.
Set the buck converter to 5.0 V with a multimeter before connecting the ESP32. An adult handles the lithium pack and SIM. This is a test prototype; keep a real collar light for your pet.
Strictly follow the description given with this video.