I have never used an i-Button, and know very little about them, I have seen a couple, but they are not very popular where I am, but again from what I have seen they seem to be popular in Russia, IF WE ARE TALKING ABOUT THE SAME THING
i-Button , I THINK is a product, which uses a contact terminal for access.
Which is why we ( well me at least ) wont be too familiar with them, if we can’t install one under our skin, it is not really something we ( I ) am as interested in.
I am not even sure if a Proxmark will work with it but I do know that a Flipper Zero can / will
Here is some info
If you don’t get any more replies, I will do a little research and see what I can find out
here is a quick couple of things
Is there a reason you are interested in i-Button in particular? Is there something else available that will achieve what you want?