This is a beautiful example of the wrong way and right way to do things.
If you add a kernel ability to do an ioctl on console of "wait for blank"
you can put the rest in user space. Instantly you gain flexibility, a blanker
that wont break the computer, and the ability for other programs to watch
for blanking easily.
The alternative is a nasty hack in the console drivers, a pile of device
specific kernel modules and no gain to other programs.