We learned from Debbie (of Debbie and Olivier's One Window House) that to really cut down on heat indoors, you have to block the sun before it gets through the windows and into the house. Even if you have reflective or solar shades, if they're on the inside of the window, there is still heat being trapped inside (this is why awnings can be a big help). These shades when hung on the outside of a window could really help things stay cool inside.
In addition to keeping things cool inside, these would also be a great way to have privacy outdoors. Gregory had a great post about outdoor tension rods and drapery for his al fresco dining plans and we think these roll up shades would be great to help section off a portion of the patio or to close in a porch that get's too much sun to sit in comfortably. Coolaroo Window Shades are made of all-weather knit fabric and block up to 90% of the sun's UV rays but will still let light and air pass through. The fabric will resist mold, mildew and rot so it's made for the outdoors.