I’m using simplex without problems. I get all notifications and didn’t notice an increased battery drain.

It’s technically viable, using a distributed hash table for example. But I’m not aware of any solution that does it.

Sadly, they are doing it in spain, the judges recently stated that they can do it, and few days later almost all of the spanish newspappers had it.

Yes, you can only use it if you where using it in the past, sadly the project seems to be abandoned.