***** the SonarPen Calibrate app is needed the following app to work properly: Flipaflip Medibang Paint Spacedesk HiPaint The official calibration app for the SonarPen, compatible with Android phones, tablets and Chromebooks. This app calibrates and optimizes your SonarPen to your device for gradual pressure sensing, pen stroke smoothness through a guided multiple step process. Compatible with SonarPen supporting apps. ****For bugs or issues, please let us know via [email protected]. Your feedback is appreciated. Permission requirement: Record audio - SonarPen communicates with the phone through audio channel Access photo, media and files - to save the calibration setting Network access - to download pre-calibrated settings from the SonarPen server