Just the cable (which is only made for the watch so if you lose it you'll have to buy a new one) but which has a USB plug and can therefore be charged on a USB port on a computer or any smartphone charger.

You talk about android, but do these functions (call notifications, WhatsApp, ...) also work with an IPhone?

Only a USB cable is needed. The charger is not necessary.

A dedicated cable, supplied with. (USB port)