Just took delivery on the $40 Griffin Survivor...I'm impressed...totally bombproof.
The case is not bulky, weighs 1.9 oz, the tether 0.1 oz, for a total of 2 oz. The sound quality for the cellphone is excellent, not much muffling observed. Claims to be waterproof to 10 ft, and dropproof to 6 ft.
The design and features of this case is well thought out. Comes with a 70 page (!) owner's guide, that takes you through initial immersion test sanity check. 1/2 of it is not in english.
The $10 Seattle Sports DryDoc in the above post, weighs less than an ounce will take care of most of my trips. However, where immersion is a high risk on a trip, such as stream/river crossings, I'll ante up the extra oz, and take Griffin Survivor.