It's fairly easy to detect if a unit uncloaks. However, determining when it DOES cloak is a bit harder. The principle works like this:

You have a computer owned ground unit in the top right corner, with a location placed over it. The player owning the ghost must be unallied and the ghost cannot be invincible. A constantly trigger detects if the computer unit is in that location. If it is, it runs AI script "Send all units on Random Suicide Missions". If the ghost is uncloaked, it can "see it" via computer's cheap ability to see the whole map, and it tries to leave the location and attack. If it is cloaked, it will just sit there.

When it leaves the location it is important to return it to the location so it can't actually find the ghost and kill it (you can enclose it with DTs if you want).

Now detecting cloaking, rather than uncloaking is a bit more complicated. In this system, every time the computer unit is in that location, a death count is added. Every time it leaves the location it is reset to 0.

Now an important thing to note is that a certain amount of death counts will be reached before it is reset (I believe it is determined by unit size + speed). It is important to find out the number for the unit you are using (a devouring one/upgraded zergling is the best unit to use, as it is very fast). You set the number that determines if the unit is cloaked (the computer unit will be still) one death count higher than this number.

For example, when a devouring one tries to leave the location it can reach 3 death counts. So, if it isn't moving the computer's death counts can reach 4, and the unit is cloaked. Then you can use this however you want (make sure to reset energy when the unit is not cloaked).

This could probably be used with wraiths as well.

Is the whole deathcount thingy for the unit being in the location? If you use an inverted location, there can be a 1px coordinate that is the ONLY area the unit will be detected (even being 1px off center will make it not in the location.)

Wraiths are the very same as well.

Wouldn't this require having a computer completely given over to cloak detection? since random suicide missions is a full AI, rather than just at a location?

And wouldn't it go after other units owned by you...

Yeah, it is something of a one trick horse, you will need to dedicate an entire player for each cloaked unit.

The main use I could think for this is for an RPG or single-player map, where a player controls their actions via a ghost.

I think it's fairly useful in an RPG situation where you don't want your main unit to look like an evil worm (Defiler) or be a ship (corsair).

Oh, and on an unrelated note: I can't seem to disable nuking capability in SCMDraft, I've tried disabling both nukes and their silos and neither does anything (there is still the greyed out option).

I made a map that detected cloaking for a friend a while ago.

Here it is.

Attachments:

Lethal, I opened that map and placed a marine and then it couldn't cloak because there was a different unit that the wraith would always go after.

That doesn't matter in this case, since Wilhem is making a one-unit-per-player map.

People seem to miss my point: this is intended for RPGs/arena maps, etc.