It is an application for amateur radio CW beginners.
Your smartphone will work as a CW-QSO partner.
If you touch the START button, your smartphone will call you with CQ, so please answer!

App settings
Callsign: Callsign on the smartphone side
Auto: When checked, a callsign is automatically generated each time.
Speed: CW transmission / reception reference speed setting (WPM)
Tone: CW side tone frequency setting (Hz) sent from the smartphone side
TX: CW message sent by you
RX: CW message received from smartphone
START: Start QSO
STOP: Cancel QSO
* There is no side tone function on the transmitting side.

About the response to CQ
Start with DE, like DE JA7XXX. No call sign is required on the smartphone side. If you send a message that contains the following keywords, it will react to it.
QRA, NAME, QTH, WX, RIG, ANT, RST, 73