MyTaxi still available in Rome?

Yes it still exists, but it is now called FreeNow

However ItTaxi app is even more popular now. And they paired up with Uber last summer, so you can use them interchangeably to summon taxicabs.

Are those apps only for Rome or all over Italy? Thats really good to know.

Nationwide.

ItTaxi is the app of the Italian RadioTaxi Association. FreeNow (formerly MyTaxi) is a German mobility service app that operates in several countries including Italy.
ItTaxi and Uber have partnered last September, so you can use the two apps interchangeably in Italy. Not sure if for now the Uber works only in major cities. In any case if you use the Uber app (or ItTaxi app) a regular taxicab will come to you, not a regular guy on his own car like in the US. That type of service provided by unlicensed private individuals is not permitted by Italian law.

Thank you Roberto for responding!