Stroulger developing the Pocket Sneakoscope.
A Sneakoscope is a type of Dark Detector that looks like a glass spinning top. It lights up, spins, and whistles if someone is doing something untrustworthy nearby.
History
Invention
The Sneakoscope was invented in the eighteenth century by Edgar Stroulger.
1993
Ron Weasley purchased a "pocket" Sneakoscope in Egypt in 1993 as a thirteenth birthday present for Harry. Ron's brother Bill said it was just a piece of rubbish sold for tourists and didn't work as it was whistling at their supper table. However, he had not realized that Fred and George Weasley had put beetles in his soup. (It also lit up when Ron was tying Harry's birthday package to Errol's leg, as he wasn't supposed to use the old owl for long journeys.) Later that year, Harry's Sneakoscope started whistling on the Hogwarts Express when Scabbers was nearby, as Scabbers was really Peter Pettigrew. Harry had to keep the Sneakoscope in a pair of Uncle Vernon's old socks to keep the whistling quiet.
1994
"Professor Moody" had a large Sneakoscope in his office in Harry's fourth year at Hogwarts. He had to disable it because it was extra-sensitive and was constantly whistling at Hogwarts, as there was too much sneaky stuff happening with students lying in school. However, as it could detect up to a mile away, it may have been picking up more than "kid stuff". Also, it would have been activated by "Professor Moody" himself, as he was Bartemius Crouch Jr. in disguise. When Bartemius Crouch Jr. was Alastor Moody the sneakoscope was going off all the time.
A mentioning of the Sneakoscope is briefly stated by Horace Slughorn in Harry Potter and the Half Blood Princewhen asked by Albus Dumbledore if the Death Eaters have come to recruit Slughorn:
"It's quite easy once you know how, one simple Freezing Charm on these absurd burglar alarms they use instead of Sneakoscopes and make sure the neighbors don't spot you bringing in the piano. - Horace Slughorn