Timey-wimey distress beacon

The Timey-wimey distress beacon, built by River Song, was a device that lay on top of the Great Pyramid of Giza. It existed in an alternate timeline where all of history occurred at once due to River refusing to kill the Doctor. She used the beacon to send a message across all of space and time, asking for help on behalf of the Doctor. (DW: The Wedding of River Song)