Some Dark Detectors, Foe-Glasses and Sensors.
Dark Detectors are objects than can be used to detect lying, concealment, or even when Dark Wizards or one's enemies are around. However, they should not be relied on too much, as they can be fooled.
Known Dark Detectors
Usages
Alastor Moody
Alastor Moody seemed to own quite a few of these. This is probably because of his overly cautious, and perhaps paranoid, nature. They were used by Barty Crouch Jr when he was impersonating Moody.
Dumbledore's Army
When Dumbledore's Army was formed in 1995 there were various Dark Detectors in the Room of Requirement when it served as the D.A.'s Headquarters.
Harry Potter
Harry Potter owned two sneakoscopes throughout his Hogwart's years. The first one he got from Ron in 1993 for his Birthday. In 1997 Hermione gave him a new one for his Birthday, as his old one was cracked and worn out.