The timey-wimey detector was a makeshift device used for detecting temporal anomalies by the Tenth Doctor. He used it when he was trapped in 1969 by the Weeping Angels to detect others who had been sent back in time. It looked like a late-20th century portable open-reel tape recorder with only one spool. It alerted the Doctor to an anomaly by dinging. The Doctor's vague explanation to Billy Shipton as to its function was that "it [went] 'ding' when [there was] stuff."
This "stuff" was loosely described by the Doctor as "wibbly-wobbly, timey-wimey stuff", hence the name of the device. The timey-wimey detector had one main side-effect: "It [boiled] an egg at thirty paces, whether you want it to or not." The Doctor learned to stay away from hens, as "[it wasn't] pretty when they [blew]". (TV: Blink) This device was later destroyed. (PROSE: Ghosts of India)
The Eleventh Doctor used one on an encounter with the Weeping Angels. (PROSE: Touched by an Angel)
A similar device, the Machine That Goes "Ding", also went 'ding', but only in the presence of shape-shifting DNA. Both machines also had multiple purposes, with that machine being able to microwave frozen dinners and download comic books from the future. Said the Tenth Doctor, "I never know when to stop." (TV: The Day of the Doctor)