The device transmitting to the smartphone 0 or 1. How to implement?

Question

Arduino

Task: object1 touches object2 and sends one to the smartphone. Opens, transmits zero. Tell me the idea of ​​\u200b\u200bimplementing the device, googled gps trackers, it turns out a little expensive for the function of transferring the number to a smartphone.

Answer 1

An option in the form of a button that is inserted into the headset jack. You can take out the button on the cord and place it anywhere.
You can put the reed switch on the circuit.

Answer 2

Raspberry PI3 + wi-fi + raspberry script + quickly sloppy droid program.
I already made this. wiringPi does an excellent job of detecting the closure of gpio contacts, instead of a script, it’s true that there was a program on these, but this is simply because it was easier for me. The prog-server on the phone also blinded in half an hour in Embarcadero C Builder. simply because I already had it :) The bundle worked for more than a year, after which it was liquidated as unnecessary.
PS: PI3 has Wi-Fi right on board, and driving it into adhock is elementary.