The latest bonus chapter on the OSX book site is a procfs implementation.
This is a display capture
while this is an iSight capture:
You can also inspect virtual memory mapping, information on the Mach tasks belonging to a given process, mach level user and system time counters, etc.
This is a display capture
c:~ diciu$ open /proc/system/hardware/displays/0/screenshot.tiff
while this is an iSight capture:
c:~ diciu$ open /proc/system/hardware/camera/screenshot.tiff
You can also inspect virtual memory mapping, information on the Mach tasks belonging to a given process, mach level user and system time counters, etc.