Superphone

The superphone is the nickname Rose Tyler gave to the Mobile phone that was altered by the the Doctor using "Jiggerypokery" (which he claimed mostly in jest, that he "came first in"). It has the ability to make calls through time, enabling Rose to call her Mum whilst on her adventures with the Doctor. (DW: The End of the World)

The Doctor also altered Martha Jones' phone in an entirely different way (using his sonic screwdriver rather than a technological addition to the phone) to function in a similar manner. (DW: 42)