There's a Trait in this RPG system allowing to invent us, gm's, new ways to perceive. Please post your own if you did. Here's one of mine:

Thermal vision

Creature can "see" objects in certain spectrum of temperatures through infra red wave detection. It perceives their spacial composition as well as how it's changing over time.

How it can be used

As a way to detect warm-blooded enemies - that's quite obvious. Another benefit it grants is emotion detection. When intelligent beings lie, fear or love, certain areas of their body change temperature. Character armed with Thermal vision unnatural sense can see those changes and detect hidden emotions with inhuman accuracy.

How it can be obscured

By insulating the warmth emitting surfaces. Normally thermal vision can look through clothes, but any armour that can protect from laser shot blocks it totally. It makes detection harder, but not impossible.

How does the organ giving it looks like?

Little holes in skin filled with infra-red sensitive cells.

Personally, I think Dark Sight is actually thermographic vision; it allows them to see different wavelengths of light, and a Synskin suit keeps you hidden from Dark Sight AND Preysense Goggles.

Scientific background isn't explained in this Trait. It could be thermal vision, sure, but I think that emotion reading ability is quite cool and could go in pairs with it. It's sort of "out of the box thinking" that I like.

Now for something completely different

Electric sense

Creature can sense electric discharges in it's surroundings (actually it detects magnetic fields they create).

How it can be used

Most acute senses like these can detect discharges in other creatures muscles that force them to contract. Combined with knowledge of electronics it allows to read how the cogitator processes data. The easiest way to use it is to detect powered cogitators and other tech equipment and for orientation if there's a magnetic field on the planet.

How it can be obscured

It can't really, though it's range is rather small, less than 1m.

How does it look like?

Like black freckles, each one filled with gelly substances.