add accelerometer info

Author: friadev

blog/posts/biometrics-explained.md

@@ -162,10 +162,14 @@ Model-free approaches don't try to model the human body but instead use the whol
 
 ### Accelerometer
 
-Accelerometers such as those found in your smartphone can also be used for gait recognition.
+Accelerometers such as those found in your smartphone can also be used for gait recognition. These need to be worn on a person's body so they can't be used from long distance like camera-based approaches.
+
+Accelerometers work by measuring the accelerations in 3D space in X, Y, and Z coordinates. They tend to also utilize gyroscopes, which measure the orientation of a device.
 
 ### Floor Sensor
 
+
+
 ## :material-chip: Secure Element
 
 All forms of biometric authentication rely on proper hardware such as a secure element in order to be secure. The secure element provides a secure and tamper-resistant place to store your biometric data so it can't be easily extracted. Examples include Apple's [Secure Enclave](https://support.apple.com/guide/security/secure-enclave-sec59b0b31ff/web) and Google's [Titan M](https://security.googleblog.com/2021/10/pixel-6-setting-new-standard-for-mobile.html) series of chips. You should avoid devices that lack a secure element; they won't be able to properly implement secure biometrics without one.