What are read-only wearable devices, and how do they differ from read-write systems?

A read-only wearable reads your body but does not directly modify it. An Apple Watch measures heart rate. An Oura Ring tracks sleep. A Fitbit counts activity, and continuous glucose monitors follow ...

Read-only wearable devices vs. read-write systems: How insulin pumps and more rewrite body signals

Now a new generation of devices is trying to do something the read-only wearable never could, talk back to the body.