Possible to thicken gravy without flour or cornstarch? I'm on a diet where I can't eat a number of things that I would typically use to make gravy, specifically corn and flour.  I'm planning on roasting a chicken tonight and I was thinking it would be great to have some gravy to go along with it.  

Is there anything I can use to thicken the drippings besides cornstarch/flour?

Note:
I am also not eating potatoes, soy or dairy so I can't substitute with those either.
Another  thickener that is readily available is gelatin. This has the added advantage that its free of carbohydrate (if you are avoiding that).