These are vertical mirrors, 180 centimeters or more in size, that house a computer, connect to the Internet, and also serve as a screen for streaming video.

The idea is to connect to an online coach that will appear on the mirror/screen next to your reflection.

On more advanced machines, the mirror is equipped with cameras and speakers, allowing the personal trainer to observe your movements and suggest adjustments and changes.

Users have a choice of live individual classes or group classes featuring a variety of exercises such as weightlifting, Pilates, cardio, and yoga.

In the simplest of mirrors, the video and sound are one-way – you can see and hear the trainer, but not the other way around. Classes are not typically live, but you do have access to a library of pre-recorded practice videos.

Pieces, whether the simplest model or the most advanced, typically sell for at least $1,255. Users still need to pay a monthly subscription to access video services.

The mirrors that have touchscreens are also usually equipped with several sensors connected to artificial intelligence that can provide feedback on your movements and suggest improvements.

The first mirror of this type to be sold in the UK was the Vaha. It was manufactured by the German company of the same name and was launched last year. Competing brands are Tonal, Mirror, NordicTrack, Portl and ProForm.

Vaha describes her mirror as a piece that offers “complete and immersive personalized sessions for body, mind and nutritional health.”

But is there any real benefit to being able to watch yourself train?

Colleen Logan, vice president of public relations at iFit, the US owner of Nordic Track and ProForm, says that when the user sees themselves in the mirror, “they can adjust their shape [ou sa position]to get the most out of resistance exercise and minimize mistakes that can lead to injury”.

Anthony Papathomas, a sport and fitness psychologist at Loughborough University, believes this argument is valid but admits he has some concerns.

“From a psychological point of view, training in front of the mirror image can provide important feedback, for example on running technique or weightlifting form,” he says.

“It can also appeal to people’s aesthetic motivation for exercise — you can see the muscles in action and it can be rewarding.”

“What worries me is how people who feel insecure about their body image feel about it,” he adds. “This can be a problem for those who are new to the sport and want to make a lifestyle change.

“Even among people who exercise regularly, we know that many suffer from body dysmorphia or eating disorders, and that seeing a reflection in the mirror while exercising can be distressing for them.”

A second model of high-tech mirrors is also coming onto the market: smart wellness mirrors. These are mirrors that use sensors and artificial intelligence to assess a user’s skin and underlying health condition.

The French company Care OS makes two such products that are designed to replace traditional bathroom mirrors.

These pieces use a camera and infrared and ultraviolet light sensors to analyze a person’s skin and temperature, and then suggest a range of treatments. Users can also access skin care tutorials available by subscription.

Violaine Monmarche, co-founder of Care OS, explains that the mirror works with motion and voice control.

“The bathroom is a place where people usually get their hands wet or lotion, so the mirror doesn’t work by touch — you just have to gesture in front of it,” she says.

Anoob Pakkar-Hull, Aesthetics and Beauty Doctor and Consultant at Harley Street Specialist Hospital in London, says this new technology has “the famous phrase, ‘Mirror, mirror, mine, there is – is there anyone prettier than me?

He adds: “Advancements in artificial intelligence, augmented reality and facial recognition offer a wealth of opportunities that we should leverage to empower people to assess and manage their health at home.”

However, Mr Pakkar-Hull says he still has concerns about the accuracy and lack of touch interaction. “Some medical problems require palpation [toucher] so that the condition can be properly diagnosed”.

The consultant and psychologist Dr. Elena Touroni deals with smart mirrors for fitness and wellness.

“For someone who’s already focused on perfection and maybe already sees a lot of ‘faults’ in their body, these mirrors can end up magnifying those kinds of psychological difficulties,” she says.

Psychologist Lee Chambers agrees that there is a danger that people will become obsessed with “working towards perfection.” However, he adds that smart mirrors “have the ability to reinforce health decisions and encourage health behaviors.”

He adds that the exercise mirror should also be very useful for people who don’t have time to go to the gym but still want feedback on their health.