Keychain notification sent to the app?

Question

Android

Hello. There is an application for androyd, when you click on the button in which the notification goes to the server.
Is it difficult to make a keychain with a button. So that when you click on it, a notification would also go to the server through the application?

Answer 1

https://www.alibaba.com/trade/search?fsb=y&IndexAr...
there are lots with a minimum lot of 1 piece, but of course it is cheaper in bulk,
and software compatibility needs to be checked

Answer 2

as an option: we take arduino nano or pro, gprs shield (I don’t know if there really are such on nano, if not, then on a regular arduino it will be cumbersome of course).
if the application is without authorization, then the sketch will be simple. it will be necessary to sniff what request the application sends.
UPD video with an example https://www.youtube.com/watch?v=9UEcT5GxdBk
UPD2 here is a more miniature gprs module M590-GSM-GPRS-module-development-board-learning-bo...