I am not fully familiar on how this is done, but I did find this information online:
You don’t need a
smartwatch,
fitness band, or pedometer to track your steps. Your phone can track how many steps you take and how far you walk all by itself, assuming you just carry it with you in your pocket.
Sure, fitness trackers have a lot of useful features, but if all you want is the basic stuff, your phone allows you to track those things without actually wearing and charging another device. It’s built into the Apple Health app on iPhones and the Google Fit app on Android phones
Step Tracking Works Best on Newer Phones
This is possible thanks to the low-power movement sensors included in modern smartphones. That’s why it’s only possible with the iPhone 5s and newer — older iPhones won’t have this feature. If you carry your iPhone with you, it can track how you’re moving and identify how many steps you’re taking, how far you walk or run, and how many flights of stairs you climb.
On the Android side, it’s a bit more complicated. Google Fit will attempt to work even on older Android phones, but it will work most accurately — and with the least battery drain — on newer phones that include these low-power sensors. As a Google Fit engineer
explained on StackOverFlow:
We periodically poll accelerometer and use Machine Learning and heuristics to correctly identify the activity and duration. For devices with hardware step counters, we use these step counters to monitor step counts. For older devices, we use the activity detected to predict the right number of steps.
So, if you have a new phone that has a sensor similar to the ones found in the new iPhone, it should work about as well. If you have an older phone, it will use data from other sensors to guess how many steps you’ve taken, and it may not be quite as accurate
https://www.howtogeek.com/238904/how-to-track-your-steps-with-just-an-iphone-or-android-phone/
So if these step trackers can be accessed by the phone owner, I imagine that they are available from the phone providers when obtained by a warrant. I can see how the motion sensor would count the steps, but there must be some type of location service/gps to see where these counted steps occurred.
Another interesting article that defense attorneys will love
10 Genius Ways to Cheat a Step Counter on a Phone (No Walking Required)
I’m sure
@sk716 knows a lot more about this than I do.