TelePlethy runs entirely on your device.  It doesn't have any telemetry or analytics (other than what Google puts in - see below), and my code doesn't send any data off device (except whatever you decide to save to your iCloud directory).  I don't want your information, and I have no way to get it (which is good, because then I'd have to put it somewhere and look after it).  Your data is yours.

TelePlethy uses the Mediapipe library from Google for face and hand tracking.  Google says:

 "When you use MediaPipe Solution APIs, processing of the input data (e.g. images, video, text) fully happens on-device, and MediaPipe does not send that input data to Google servers. As a result, you can use our APIs for processing data that should not leave the device.

MediaPipe Solution APIs will contact Google servers from time to time in order to receive things like bug fixes, updated models, and hardware accelerator compatibility information. MediaPipe Solution APIs also send metrics about the performance and utilization of the APIs in your app to Google. Google uses this metrics data to measure performance, API usage, debug, maintain and improve the APIs, and detect misuse or abuse, as further described in our Privacy Policy."