Bracelets can also hang on your feet and that will be already 4
but it seems to me that everything is a bit simpler, each bracelet should be synchronized with a certain phone or communicator
it will be expensive.
Yeap, one phone - one bracelet. Devs need to add a restriction on the version of Android and iOS. Creating a protection against bots when registering a new account also does not hurt.
We can invent forever. What will the developers say?