Some of you might remember those little gadgets that measured your steps (pedometers). It didn’t look cool or did much and could be fooled just by shaking it around. 

With each passing year, those little gadgets turned into full-fledged fitness monitoring devices and depending on the amount of money you are willing to spend, have a ton of tech crammed into them. So we’ve decided to break it down a little for you on what all the tech written on the back of the box means and actually does. While most devices won’t have all the tech we’re listing down in order to keep the devices as tiny as possible. The list below is getting more common in devices.

Three-axis accelerometer

3-axis accelerometer sensors are fairly common these days and can be found in almost all activity trackers. These track acceleration in 3 directions and can sense the device’s orientation, inclination, and tilt as well as take inertial measurements of position and velocity. If the device you use has a tap function, then it’s probably using the accelerometer to detect the taps as well.

Ambient light sensor

Ambient light sensors detect the amount of light in an area. It can be used indoors or outdoors and help the device either increase the brightness, so the screen is visible in a bright environment or decreases the display’s brightness if in a dimly lit room.


An altimeter senses changes in elevation using atmospheric pressure. It may be used in gauging the number of stairs you climbed but more so for outdoor watches used for hiking and tracking.


The barometric sensor tells you whether it is going to rain or not. It measures the pressure exerted by the atmosphere around it.

Digital Compass

Using a magnetometer which measures the earth’s magnetic field and combined with an accelerometer to figure out the position of the device in space. It can pinpoint the phone’s position from solid-state sensors within the device that can measure its tilt and movement. The combination of information helps display cardinal directions no matter the orientation of the device.

Digital Thermometer

Built-in temperature sensors check the ambient temperature in either Celsius or Fahrenheit. Accuracy is an issue if you need to have pinpoint measurement due to body heat.

Digital Metronome

If it’s not for music, then the metronome found in your fitness device is used for your running tempo.

Bioimpedance sensor

This is also pretty new tech and not found in traditional fitness trackers. We’ve only seen it in the Jawbone UP3 using it as a HRM. It uses less power compared to optical sensors for the same level of accuracy. Devices utilizing bioimpedance sensors capture a broad range of signals, from heart rate, respiration rate, and galvanic skin response, while still being able to be fitted into a compact form factor.

Capacitive sensor

Capacitive sensors can be used to detect and measure proximity, position or displacement, humidity, fluid level, and acceleration.
Used to wake up the device when the auto sleep mode is activated. And also used in devices to detect which part of the screen you are tapping and multi-touch.

Gesture technology

You’ve seen minority report, where all the user has to do is a swipe, pinch, and zoom to bring up different files and images. Well, that’s what this is. Of course a very primitive form of what could be. The technology here is relatively new, so it’s not a common feature even in most devices. It’s controlled by different body movements such as flicking the wrist to wake the device or moving your fingers to grab something. Much of gesture tech is still being developed.

Global Positioning System (GPS)

GPS ensures that you can find out exactly where you are on the globe. Turning this feature when turned on requires a lot of your device’s power, Which is why most devices have this feature turned off by default. Finding a signal can sometimes be hard if you are in a densely forested area, blocked by buildings or impossible if you are indoors.

Especially if you are trying to figure out where you are on a map or mapping out your routes. For the device to get a location lock, you’ll need to receive signals from 4 different satellites at the same time. Once you’ve got a lock, the device can then calculate your latitude, longitude, and elevation. If one of these variables is already known, fewer satellites are needed.


Glonass is the Russian version of GPS. Although GPS is more accurate due to it being able to pinpoint where you are on the globe using 31 different satellites vs. 24 satellites for Glonass overall, but due to the different positioning of the GLONASS satellites, GLONASS has better accuracy at high latitudes.

(meaning you get better accuracy the closer you are at the poles)


The Japanese version of GPS, but only covers Asia and Oceania.


Gyroscope sensors sense angular velocity. They help in motion tracking and improve accuracy when you are on the go. The more axes you have, the better.

Sleep Trackers

Wrist-worn sleep monitors use a measuring tool called actigraphy. It involves using the accelerometer in your device to measure the amount of movement you are producing. The idea here is that a certain degree of movement corresponds with being awake, and periods of stillness corresponding with being asleep. The manufacturers of the device then may up with an algorithm to determine the stages of your sleep cycle and the amount of Zzz’s you get.

LTE (Long-Term Evolution)

Very few fitness trackers have an independent cellular signal, and most are dependant on a mobile device for full functionality. Also not until recently squeezing a sim card into a smartwatch just bulked the watch up to much and drained the battery. This, of course, will change as Samsung and Apple have come up with smartwatches that do not need to be tethered to a mobile device.

Optical heart rate monitor

The optical heart rate monitor uses light shone against the skin. During activity or non-activity the blood moves through your veins at different rates. Using pulse oximetry, it takes advantage of the fact that oxygenated and deoxygenated hemoglobin have different optical properties. With every heartbeat, there is a spike in arterial (oxygenated) blood, which is detected as a change in the absorbance and reflectance of red and/or infrared light.

UV sensor

UV sensors in fitness trackers alert you when you may be absorbing too much UV radiation.

There are of course other tech being developed or are already in use. But for brevity, we won’t shine a light on those as they are far too uncommon.


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