On a stifling day in Tokyo, a journalist clamped a small, curved device to the back of their neck. The sensation, they later wrote, was “like having a permanent ice pack glued to the back of your neck” – a sudden, intimate chill that radiated down the spine. It was not a medical patch but Sony’s reon pocket pro plus, a wearable air conditioner designed to sit beneath a shirt collar and cool the body directly.

Unlike a handheld fan that merely blows air, the device uses a thermoelectric cooling plate to lower skin temperature. It targets the upper spine, where blood flows close to the surface, and vents extracted heat upwards through an exhaust outlet to prevent it building up beneath clothing. Sony claims the new model runs 2C cooler than its predecessor and fits more securely, thanks to a widened neckband and flexible hinge.

The gadget arrives as another heatwave bears down on the UK, and Tokyo swelters, sending shoppers scrambling for any appliance that promises relief. Alex Baldock, chief executive of Currys, warned earlier this month that fans and portable air conditioners had been “flying off shelves nationwide”. Yet many common cooling practices are ineffective. Air conditioning specialists note that setting a thermostat to 16°C does not cool a room faster than setting it to 24°C or 25°C; the thermostat merely sets a target temperature, not the speed of cooling. The US Department of Energy recommends keeping the thermostat at 26°C (78°F) when the home is occupied.

Portable air conditioners, while effective, are bulky and heavy – even compact models weigh more than 20kg – and cost considerably more to buy and run than fans. The wearable alternative, though still pricey, offers a personal cooling zone that follows the user. The Independent’s tester found it stayed glued to the skin during walks and train rides, only shifting occasionally, and noted that wrapping the arms further around the neck helped, though it sometimes felt “a little like a chokehold”.

On the hottest days, the device’s quiet hum and the ghost of an ice cube against the skin hint at a future where personal microclimates might become as ordinary as a pair of headphones. As it cools the body, it exhales a faint stream of warm air upwards, a tiny, private weather system beneath the collar.