Hi ! Thank you @cyprianj :)

For these small packages the price does not vary depending on the destination according to the post office website.

I tested the autonomy on the previous version and the leds were on for about 24 hours in a row. The badges use CR1220 3V cells batteries which are very easy to find.

The badges do not have switches for the moment but I have already ordered some to test, as lemouth said for the moment you have to remove the battery