Aura Strap 2
Boost your Apple Watch with Aura Strap 2, the ultimate health tracker offering precise body composition analysis to help you reach your fitness goals.
Boost your Apple Watch with Aura Strap 2, the ultimate health tracker offering precise body composition analysis to help you reach your fitness goals.
AURA Strap 2 turns your Apple Watch into a portable body-composition tool that’s great for tracking trends in fat, muscle, and hydration over time—so long as you respect its BIA limits and keep your measurements consistent.
Select Color
AURA Strap 2 is a replacement band for the Apple Watch that adds bioelectrical impedance analysis (BIA) to your wrist. Instead of stepping on a smart scale, you touch the strap’s stainless-steel electrodes for roughly half a minute and get estimates for metrics like body fat percentage, muscle mass, visceral-fat index, bone mass, and total body water. The big idea is convenience: the device lets you take readings anywhere, right when you’re thinking about your training or diet, and then see those results alongside your everyday activity data.
This second-generation model refines almost everything about the original. The strap is slimmer and more comfortable, connectivity switches to Bluetooth Low Energy for faster, more reliable syncing, and the sensor captures more raw data per reading. The companion iPhone and Apple Watch apps visualize your measurements and sync them with Apple Health, so your composition trends sit next to your workouts, steps, and sleep data in one place.
The Strap 2 looks like a sport loop at first glance, with soft silicone that stretches slightly to slip over your hand. It ships with multiple sizes in the box (S, M, L, XL), which matters more than it sounds: a proper fit keeps the electrodes stable on your skin and avoids noisy measurements. The clasp is fuss-free, the underside is smooth against the wrist, and there’s a small status LED that confirms when a reading is in progress.
Compared to the original Aura band, this model is roughly a fifth thinner, which helps it disappear during daily wear. It’s built to match Apple’s design language reasonably well, so it doesn’t look like a medical device bolted onto a watch. Materials are pragmatic—silicone for the loop, medical-grade stainless steel for the contact surfaces, and a plastic housing for the electronics. Water exposure from daily life (like hand-washing or light splashes) isn’t a problem, but as with any BIA accessory, you’ll want to avoid soaps, salt water, and high-velocity jets which can degrade materials and lead to unreliable readings.
Power comes from a replaceable CR1632 coin cell. With typical use, battery life stretches to months rather than days, meaning you won’t be charging yet another gadget every night. When it’s time to swap the cell, the process is straightforward and doesn’t require re-pairing.
BIA sends a very small, imperceptible electrical current through your body and measures the impedance—how much the body resists and reacts to that current. Because fat, muscle, bone, and water conduct electricity differently, the device’s algorithms can estimate the proportion of each.
Most BIA scales send the current foot-to-foot; the AURA Strap measures wrist-to-wrist through the upper body. That difference matters. Upper-body composition can skew differently from your legs and hips, so you should expect absolute numbers to differ from a bathroom scale or a clinical DEXA scan. That isn’t a deal-breaker; the strength of BIA is in its repeatability. If you measure in the same way, at the same time of day, under similar conditions, the relative change—the trend line—is what you can trust.
Key metrics you’ll see include:
AURA cites higher raw-signal density in this model and reports strong correlation against gold-standard methods under controlled conditions. That phrasing—under controlled conditions—is worth emphasizing. No wrist-worn BIA gadget replaces clinical tools; used correctly, it’s a personal dashboard for directionally correct insights.
Setup happens in the AURA iPhone app. You pair the strap over Bluetooth, enter basics like height, weight, age, and sex (which influence the algorithms), and pick your goal targets. On the watch, the AURA app guides you through a short posture tutorial:
Do this at a consistent time—many users choose first thing in the morning, before food or training. Avoid readings right after workouts, saunas, hot showers, alcohol, or big meals; all of these can swing your hydration and skin temperature and skew results. If you’re tracking a program, stick to the same protocol every day and look at the trend lines rather than individual points.
Results appear instantly on the watch and sync to your phone. The app’s standout visualization is the Biogram, a quadrant plot that maps fat and muscle together so you can see whether you’re moving toward more muscle and less fat, or vice versa. Historical charts let you zoom out to weeks and months, which is where the strap’s value becomes obvious.
All BIA devices live and die on consistency. Here’s how to get the most out of the Strap 2:
When used this way, the Strap 2 is a solid trend tracker. You may still see random outliers—usually on days when you deviated from routine—but the rolling average lines smooth these bumps. For athletes and strength-training enthusiasts, the muscle and water signals are especially helpful for periodizing nutrition and tapering.
The AURA app is clean and purposeful. The home screen surfaces your latest reading with context (“up 0.2% body fat from last week”) and quick charts. The Biogram provides an at-a-glance view of body-recomposition progress, while deeper pages break out individual metrics with ranges and multi-week trends. You can tag readings with notes like “post-leg day” or “travel day,” which is handy when interpreting spikes and dips.
Data syncs to Apple Health, so your body-composition metrics can sit alongside your rings, workouts, and third-party logs. If you share Health data with a coach or a different app, AURA’s numbers piggyback across. There’s also a Guest mode for one-off checks on friends or clients without polluting your history.
AURA sells an optional AURA Plus subscription that layers on more analysis, monthly reports, and curated training and nutrition content. The free tier is perfectly usable for self-guided tracking; Plus is worthwhile if you like coaching cues, deeper trend interpretations, or printable reports.
Switching from the original model’s acoustic (ultrasonic) sync to Bluetooth Low Energy is a meaningful quality-of-life upgrade. Pairing is simple, reconnects are fast, and readings land on your watch immediately. Drops are rare and typically clear by re-opening the watch app.
Battery life is measured in months, not days. The CR1632 coin cell is inexpensive and easy to find; swapping it takes a minute and doesn’t require re-pairing. Durability is good for daily wear—commutes, office, gym sessions. As with any accessory that relies on skin contact, clean the electrodes occasionally to keep readings stable.
Who should skip it? If you rarely look at metrics, don’t wear an Apple Watch, or only care about the number on the scale, a simpler tool (or nothing at all) may suit you better. Likewise, if you need medically diagnostic accuracy, talk to a clinician about DEXA or other gold-standard assessments.
The strap is a one-time hardware purchase, with an optional subscription for deeper analysis. If you love guided insights and structured content, the subscription is easy to justify. If you’re self-directed, the free tier’s charts and Biogram cover the essentials. Either way, the real value comes from consistency over months: tiny, daily data points that add up to a clear picture of change.
Pros
Cons
AURA Strap 2 succeeds by making body-composition tracking effortless. It doesn’t claim to be a medical device, nor does it need to be: its job is to give you consistent, directionally accurate feedback so you can adjust training, nutrition, and recovery with confidence. If you already live in the Apple Watch ecosystem and care about what your body is doing—not just what the scale says—the Strap 2 is a smart, surprisingly frictionless upgrade.
Buy for $159