Apple Watch’s Wireless Functions and Internal Sensors

By Marc Saltzman

Oh, Apple Watch, you cleverly hide so much of your magic under your skin. While Apple isn’t revealing much about the “brains” of Apple Watch — a system-on-a-chip called the S1 — a more interesting dissection is perhaps all the other goodies that make Apple Watch a fully functional wearable.

Apple Watch indeed houses a good number of wireless radios beneath its surface, including Bluetooth, Wi-Fi, GPS, NFC, and more. To better understand what they do, consider the following.

Bluetooth 4.0

Bluetooth makes a local wireless connection between two or more devices. Just as your wireless headset is paired with your smartphone so you can make hands-free calls, Apple Watch wirelessly communicates with a nearby iPhone. This lets you see texts on your watch, receive phone calls, control your music on your phone, and more. Bluetooth 4.0 works with devices up to 200 feet away (compared to just 30 feet with earlier versions).

Wi-Fi 802.11b/g

Apple Watch also features Wi-Fi, which gives it online connectivity — even when no iPhone is in sight. As long as you’re on a wireless network, such as your home’s Internet connection or a coffee shop’s hotspot, you can access such information as email, live sports scores, mapping information, and so on.

A feature called Continuity — introduced in iOS 8 — means you can also receive messages and take calls on multiple iOS devices (such as answering a call on your iPad) as long as you’re in range of your Wi-Fi network — and Apple Watch can do this too.

NFC (near field communication)

NFC is a short-range radio technology (like Bluetooth) that has a number of applications but is most commonly associated with mobile payments. Similar to waving or tapping your iPhone 6 or iPhone 6 Plus on a contactless terminal at retail locations (or a compatible vending machine) to make a secure purchase, Apple Watch also uses NFC to make a digital handshake with the terminal to complete the transaction.

Yep, it’s all in the wrist. This is part of Apple Pay, Apple’s mobile payment solution for secure cash- and card-less payments.

GPS (on the iPhone)

While Apple Watch doesn’t have GPS, it works with the iPhone’s GPS chip to identify its location on Earth — down to a few meters of accuracy. Therefore, when coupled with mapping applications, GPS can help you see your location on a map, get directions from point A to point B, look for local businesses of interest, and more.

GPS can also help with tracking fitness data when measuring steps won’t help (such as in cycling). Along with the accelerometer, built-in heart rate sensor, and Wi-Fi, Apple Watch’s GPS can help measure distance traveled.

Accelerometer

As with other smartwatches and activity bands on the market, Apple Watch has an accelerometer that measures movement — whether you’re lifting the watch to your face to turn on the screen, lowering your wrist to not accept a call, or calculating fitness activities, including your steps taken (like a 21st-century pedometer), total distance traveled, time spent exercising, and estimated calories burned.

Heart rate sensor

A custom heart rate sensor included with Apple Watch helps gauge your intensity during exercise and improves overall calorie tracking. It listens to your heart’s beats per minute (BPM) and shows you data on the screen — if and when you call for it. Behind the watch are four sensors that measure your pulse through your skin.

Going beyond fitness are the fun applications too, such as sharing your heartbeat with someone — felt on his or her Apple Watch — to show you’re thinking about that person.