This is a great question! Since his beatification in 1990, Blessed Frassati has been unofficially declared the patron of students, Catholic youth, mountain climbers, skiers, Dominican tertiaries and much more. But the only official recognition given him by the universal Church is as patron of Italian Confraternities and for certain World Youth Days.
Actually, because Pier Giorgio is not yet canonized, the Church restricts public veneration to the local dioceses closely associated with his life such as Torino or Biella in Italy. We are free to privately venerate him, however, on an individual basis.