SonarPen is a $30 iPad stylus that connects to the headphone jack - The Verge

An affordable alternative to the Apple Pencil

SonarPen USB Type-C to 3.5mm Headphone Jack Adapter

平板配件｜SonarPen不插電智慧感壓繪畫筆，低成本入手- 鹹魚爸的3C新奇

SonarPen Is A Smart Stylus That Works With Any iPad - iOS Hacker

Stylus Pen for iPad with Palm Rejection Active Pencil FOR Apple

This pressure-sensitive stylus makes almost any iPad mimic the

SonarPen is a $30 iPad stylus that connects to the headphone jack

SonarPen users

SonarPen stylus review - The Gadgeteer

SonarPen stylus review - The Gadgeteer