What are Liquid Crystals Good For?

Uses: 

          LCD:
(Liquid Crystal Displays) for watches, clocks, computer screens:

Liquid Crystal Displays (LCDs)

Molecules that organize forming thread-like structures (Nematic) that align with each other, and cooperatively change direction when an electrical or magnetic force is applied. 

Thermometers:

Liquid crystal thermometers

Cholesteric molecules that organize forming layers whose relative orientations is helical, with a pitch similar to the wavelength of visible light.  This pitch is very sensitive to changes in temperature to produce different colors.

             Helmets and Bullet-proof vests:
 
 

Made into ultra-high strength fibers like Kevlar

Long-chained rigid polymers that orient parallel to each other, with very strong inter-molecular interactions, strong enough to withstand the impact of bullets.
 

 Battery testing strips (used by DuraCell) 

Charge indicator for batteries. The principles for this application is similar to that used by liquid crystalline thermometers. Electrical current passing through the media generates heat. The change of relative orientation of the layers produce a color change.

              Slugs and Snails (nature)
Nature beat us to the punch in making use of liquid crystals. The mucus secreted by slugs behaves like liquid crystals. Its rod-shaped molecules align in varying degrees to control the viscosity of the mucus to adapt to different ground conditions. 

Liquid crystals can also be found in biological cell-membranes.