Keyboard Emulator for Seiko UC-2000

Experimental application for Android. Phone speaker is used as an Induction coil to transmit data to the watch.

Unfortunately, this does not good work on all phones, I tested app on Nexus 5X (on video) - very good (only 10-20% of errors), Galaxy S8 - medium (with good positioning - 30-50% error), Nexus 5 - medium (with "antiphase" options)..
With a very poor connection, you can try to remove the back cover from the watch.