H-M-H/Weylus

turns your tablet or phone into a graphic tablet or touchscreen for your computer

screen annotation tool for Windows, macOS, and Linux
DmytroVasin/DrawPen
note-taking app with stylus support, pressure-sensitive inking, and low-spec device compatibility
alpha-liu-01/SpeedyNote
turn any device with a browser into a second screen
pavlobu/deskreen
Turns touchpad or touchscreen gestures into custom desktop actions on Linux
JoseExposito/touchegg
heart rate from fingertip using phone camera
richrd/heart-rate-monitor
multi-device drawing board with creative brushes
LHRUN/paint-board
virtual monitor app for easy screen sharing
Stengo/DeskPad
USB device for security testing, payload delivery, and pentesting automation
i-am-shodan/USBArmyKnife
lets you make iPhone and iPad apps on Mac look sharper with bigger text
cormiertyshawn895/PixelPerfect
portable computer for coding, music, and projects with a touchscreen and sound
shorepine/tulipcc