sniffMK is a simple utility designed to sniff mouse and keyboard events on macOS. It is based on code from amit singh's website; (http://osxbook.com)
It was designed to facilitate malware analysis (specifically OSX/FruitFly which can simulate both mouse and keyboard events - see BlackHat/DefCon slides for details).
Run sniffMK, as root, to start sniffing events:
# ./sniffMK
mouse/keyboard sniffer
based on code from amit singh (http://osxbook.com)
event: left mouse down
x: 821.285156
y: 727.726562
event: left mouse up
x: 821.285156
y: 727.726562
event: key down
key modifiers: shift
keycode: 0x4/h
event: key up
keycode: 0x4/h
event: key down
keycode: 0x22/i
event: key up
keycode: 0x22/i
....
event: key down
key modifiers: control
keycode: 0x8/c
To only capture mouse events, execute sniffMK with the -mouse commandline argument.
Similarly, execute it with the -keyboard commandline argument to only capture keyboard events.