Product test

A polarising ring: no subscription and a good app – but with weaknesses

Lorenz Keller
8.7.2025
Translation: Patrik Stainbrook
Pictures: Lorenz Keller

Affordable, a sleek app, no subscription: this smart ring from Indian manufacturer Luna surprised me with quality features, despite a bumpy start to the test.

Talk about shock while unboxing! Is my ring damaged? I like the stylish packaging of the gadget, reminiscent of jewellery or watch manufacturers. But when I hold the ring for the first time, I get the feeling something’s wrong. The matt black ring is stained and has a bulge. At first, I think it could be a production error.

The unevenness on the top of the ring confused me at first.
The unevenness on the top of the ring confused me at first.

Fortunately, I took a closer look at the product images. The slanted unevenness, something between a wave and a crease, is a striking and unusual design element. Fortunately, the discolouration can be wiped off with a microfibre cloth. Turns out it was adhesive residue from the plastic film that protects the ring until it’s unpacked.

The design is both an opportunity and a risk for the manufacturer. Luna does stand out from other smart rings, but the look is polarising. It took me two weeks to get used to it.

By the way, ordering the Luna smart ring worked well. I used the sizing kit to determine my right size in advance. Size 11 fits perfectly on my middle finger. It’s worth trying out the plastic model for a few days before buying a ring so that it’ll fit comfortably but won’t be too loose for tracking data via the sensors.

After-sales service test thanks to a battery problem

Unfortunately, my tricky start didn’t end here. Installation went smoothly, but after almost four days the ring’s battery was suddenly flat. I couldn’t recharge it any more either.

Was I doing something wrong? Could I reset the ring? I wrote to customer service without much hope of a reply. More specifically, there’s a chat function in the app under the menu item Live Support. After an hour, I got a reply with instructions on what I could try. The problem’s analysed step by step, I sent screenshots and a video.

Support can be reached quickly and easily via the app.
Support can be reached quickly and easily via the app.

I’m pleasantly surprised at how seriously I was taken and how quickly the support team responded. When all else failed, I was offered a replacement without any fuss. The Swiss importer, whom I’d already contacted, took care of this. Nevertheless, it’s good to know that the Indian manufacturer provides good customer service.

I was probably just unlucky and got a faulty model. My second ring runs and charges perfectly. I also took the opportunity to order a second of the five colours – glossy silver instead of matt black. On that one, there’s less adhesive residue from the protective film – and the characteristic wave is also more discreet.

In shiny silver, the design is somewhat less conspicuous.
In shiny silver, the design is somewhat less conspicuous.

Comprehensive tracking without a subscription

With this second ring, I was finally able to enjoy the fun features – such as its modern and stylish free app. The manufacturer has dispensed with a subscription model: you only have to buy the ring for around 300 francs and can then use all the features without restrictions.

The Luna ring offers the usual movement and sleep tracking in this category. It measures steps, pulse, skin temperature and blood oxygen. This data is displayed clearly using graphs in the app.

The app is clearly laid out and yet fun to look at.
The app is clearly laid out and yet fun to look at.

Luna calculates various parameters from these measurements, such as your stress level or «Readiness». It’s a score for your fitness and well-being that includes a sleep assessment, exercise, recovery and heart rate variability (HRV).

The system is active: I always receive tips and hints, including notifications if required. The app tells me when I should and shouldn’t drink caffeine or the ideal bedtime. I do notice how strict Luna is, immediately sounding the alarm on a night with little sleep, for example. Depending on your personality, this can be more likely to motivate you to change your behaviour than the competition, which simply displays data.

The sensors in the ring measure movement and pulse.
The sensors in the ring measure movement and pulse.

I can only judge how accurate the tracking is based on my everyday experience. The sleep tracking system recorded the exact times at which I fell asleep and woke up. This ring recognises even light workouts such as hiking or walking and displays them in the app. I still have to confirm these values.

One place the Luna ring does perform poorly in is counting steps. I walked 1,000 steps twice, counting them by hand with a clicker. Compared to the competition, Luna’s values are just too high: a 13 per cent deviation is twice as much as the competition.

How good’s the AI?

Luna is one of the first manufacturers to offer artificial intelligence for additional data analysis. You can call up a daily health overview here. Luna AI also suggests questions to ask. It isn’t just for analysing data, it also explains various terms or functions.

This was useful initially, when technical terms like HRV or circadian rhythm didn’t mean anything to me yet. I also asked questions freely, for example: «Which sleep values should I improve?» This way, I learned my REM and deep sleep phases could be better. The app recommends I relax before going to bed, keeping the bedroom dark and cool too.

Unfortunately, Luna AI only interprets part of the data; it’s more helpful when explaining and giving tips.
Unfortunately, Luna AI only interprets part of the data; it’s more helpful when explaining and giving tips.

The answers to various questions are rather general and brief, but can certainly be useful. Just a pity that the AI only accesses my daily measurement data, with no analysis over days or weeks.

Comprehensive data protection and privacy provisions from Luna manufacturer Nexxbase can be found on their website. The Indian company appears to use its own AI model, guaranteeing compliance with European data protection standards – but the company stores and processes its data outside of Europe. Nevertheless, a renowned cloud provider was chosen in the form of Amazon.

Still, you’ll have to trust the manufacturer to really adhere to its own specifications and not misuse your health data.

Weaknesses with the battery and charging

Luna tracked my life across seven days on one charge. After that I had to plug the ring back in. Although the battery life is longer than that of many smartwatches, it’s still below average for a smartwatch. The Samsung Galaxy Ring, for example, lasts seven to eight days, the Oura 4 seven and a half. The competition from RingConn even stays on for nine to ten days.

The charger only works if the ring is positioned exactly right on it.
The charger only works if the ring is positioned exactly right on it.

The charger is a simple dock, and the manufacturer has dispensed with a useful charging case. The dock only fits one ring size – and there’s exactly one position in which the gadget actually charges. As a result, I have to make sure the line printed on the inside of the ring is exactly on the mark while using the charging dock. A pulsating LED light shows me when the ring is supplied with power. It works. Fiddly, but it works.

From a difficult start to my test, highlights in the app and AI, but also a mixed result in terms of accuracy and battery life, the Luna Ring has a hard time standing out positively from competition like Oura, Samsung, Ultrahuman or RingConn, which are already established in Switzerland.

In a nutshell

Smart helper, bad battery

This smart ring from Indian brand Luna has clear strengths, but also a few weaknesses worth mentioning. Its eye-catching look with that wave on top is polarising, and the one-week battery life is definitely below average.

The app, beautifully designed and clearly laid out, does impress. An AI assistant helps you evaluate and understand the various measured values. The system gives plenty of tips and instructions – it’s also quite strict if you don’t get enough exercise or don’t keep to your sleep schedule. You don’t need a subscription for these detailed evaluations – everything’s already included in the purchase price of the ring.

Pro

  • Exceptional design
  • Fair price without a subscription model
  • Smart and clear app
  • Good chat support

Contra

  • Unique design
  • Inaccurate step counting
  • No charging case

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Gadgets are my passion - whether you need them for the home office, for the household, for sport and pleasure or for the smart home. Or, of course, for the big hobby next to the family, namely fishing.


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