I am new to the awesome world of making and electronics. I want to do a project to help me keep from losing a small item frequently. I need a transmitter and reciever that are very small. I would like to have it where when the transmitter and reciever get more than 25 or 30 feet away an alarm will sound. One of the pieces is about the size of a quarter and the other would need to be about the size of a credit card and no thicker than 1/4 inch. I would need to enclose them to be waterproof or at least water resistant. Does anyone know what items would work for my application?
Search for “electronic child leash”.