I am considering purchasing a EWA housing for dusty conditions. Is there a way to import sound to my GL2 while encased in this housing? Will a remote mic penetrate the EWA housing?

According to the web site:

DO CAMCORDERS PICK UP SOUND INSIDE THE HOUSING: Yes. The loss of sound is only about 5 %. By moving closer to the subject, sound ( voice ) will be easily heard without distortion. Underwater, the sounds of bubbles ( from breathing apparatus ) or noise from friendly dolphins can also be heard.

But for just dusty conditions, without the water conduction, I would have my doubts.

How about a Kata cover? It's not nearly the seal the EWA or similar units provide, but you have real access to the controls and the lens and mic are not covered by plastic.