Emergency Program One

Emergency Programme One was a feature of the Doctor's TARDIS designed to return a companion to a designated place in case of extreme emergency (DW: The Parting of the Ways)

The Tenth Doctor mentioned that Emergency Programme One was automatically activated after five hours. (DW: Silence in the Library) When activated, it projected a hologram recording which explained the programme. (DW: The Parting of the Ways)

Believing that he would die on the Game Station, the Ninth Doctor used it to play a message for the benefit of Rose Tyler before the TARDIS returned  Rose to her home of Powell Estate in 2006. (DW: The Parting of the Ways).

Donna Noble recorded a message on it as a way to say goodbye to the Tenth Doctor, in the event that she might not have a chance to do so herself. (DWM: The Time of My Life)