It seems there is still 6 months before implementation is ready though.
A few months ago when this was announced some officials said there would be a system for WNA (tourists and investors specifically mentioned) to register foreign phones, but I haven't seen any recent news about that.
It says phones with foreign SIM cards are exempt from registration. My provider (t-mobile) has an inexpensive text & data roaming agreement in Indonesia, so my phone should work without registration, at least in theory.
This is all about tax income and shoring up local smartphone sellers.