Most fitness trackers sit politely on your wrist, but Pavlok doesn鈥檛 play nice. You might call it Fitbit鈥檚 evil twin or the bad cop to the Apple Watch good cop.The wearable technology provides a small electric shock that its creators say can help curb smoking, eating doughnuts and watching too much TV. 鈥淓arn rewards when you succeed. Pay the price when you fail,鈥 said a for the device.

鈥淭here鈥檚 a real power in using a to help you break your bad habits,鈥 the creator Maneesh Sethi said on ABC鈥檚 Good Morning America when the wristband was first released in 2014. Sethi appeared on the business-pitch reality show in 2016 but declined an offer from Kevin O鈥橪eary. The second edition of the Pavlok bracelet was released in 2017 and is regularly priced at US$300. They鈥檙e for sale on for less.

Users can zap themselves with the wristband or grant a friend access through a smartphone app to remotely when caught in the act. The zap strength is no more than , according to the product website and is not enough to harm the user. Sethi said the shock, at worst, feels like the type of static shock that comes from rubbing your socks on the carpet and touching a doorknob. Still, according to some videos on social media, the shock can be pretty alarming.

A slew of testimonials on the Pavlok site claim that the bracelet has been effective. The creator has said it works in under five days. A Pavlok 鈥渃oach鈥 claimed one user became a 鈥渉yper-productive CEO鈥 thanks to his device. Various users claimed it helped them stop eating sugar, biting their nails and hitting the 鈥渟nooze鈥 button.

鈥淚 would take a sugary item I would usually eat 鈥 and I would shock myself while eating it,鈥 said one woman, claiming that after three weeks she had stopped eating refined sugar. 鈥淚 feel like I鈥檓 back in control of my relationship with food.鈥

鈥淚 shock myself every time I bite my nails,鈥 said another woman. 鈥淣ow I鈥檓 very aware and I catch myself before I do it.鈥

The name Pavlok is a portmanteau of 鈥渟hock鈥 and 鈥淧avlov,鈥 a reference to Russian physiologist Ivan Pavlov who studied conditioned responses using dogs. The basic science behind the device is called 鈥渁version therapy鈥 and dictates that repeated use of unpleasant stimulus like an electric shock in conjunction with a certain behaviour will encourage the brain to form a negative connection to the behaviour. The Pavlok website cites 21 different studies on for behaviours such as smoking, weight loss, scratching and chronic cough. The site also claims to be undergoing its own research into the effectiveness of the device.

A writer for the New York Times health blog Well posted a with the device in 2016, but it doesn鈥檛 work for everyone. In 2016, a writer for The Verge tried to use a Pavlok on her . It seemed to work at first, she wrote, and her nails even grew and stopped hurting. 鈥淏ut at the end of week one, I resumed biting my nails more fiercely than ever and I did something I found extremely liberating: I ignored the Pavlok on my wrist,鈥 she wrote. The device didn鈥檛 recognize when she was biting her nails, so she eventually chose simply not to shock herself.

The newer versions of the Pavlok claims to know when its user has their hand near their mouth to bite their nails or when their chest hits the floor in an aborted push-up.