I don't think you would want to go with the RS towel. It is made out micro-fiber I kind of odd texture which is grea for "wick"ing off moisture but not so cozy to curl up under, or eating on for a picnic.
I take something called a "quillow" it is a small lap quilt that tucks itself up into a pillow. It is very versitile as a pillow, warmth thingy and picnic or bench sitter-on. Because it is cloth it compresses well, and I usually travel fairly light so it is an extra I don't mind.
I am also lucky to have a mom who is a fabulous quilter, as such I have a conversation piece for meeting people.
In the past I have also used rain ponchos, the kind that un-snap to lay flat, or snap together for a rain coat.