“An app specifically made for the Elecraft KX3 is KX3Companion (www.kx3companion.com). There are free and paid versions on Google Play (does not work on Kindle Fire).
The same author has created KX3 KeyApp to give a virtual set of keys for KX3 users. It comes with two predefined templates (CW, and default) with KX3 macros setup for use.
Finally, he created QRSS Beacon – A fully featured QRSS (Slow CW) Beacon on Android. You can select a DIT duration from 1 to 60 seconds and choose one of the 3 supported modes: QRSS, FSK/CW and DFCW. This works on any radio, connect the audio out of your Android device to the audio in of your radio and an enable VOX.
Also, HamLog is available on iOS & Android (there’s even a MAC version).”