One of the anticipated Molecular Nanotechnology systems I find exceptionally useful is 'Utility Fog'.
Utility Fog is a swarm of invisibly small molecular robots, programmable to rearrange into virtually any configuration, almost instantly. These links will give you a good understanding of the concept:
An enormous range of possibilities could be realized with this highly adaptive technology, . Depending on the need, the swarm could be any size... from a few molecular layers to hundreds of yards thick. I visualize Utility Fog as a personal tool... an extension of human capabilities... surrounding and interacting with its user. The user would neither see nor feel the swarm, until formed into solid or opaque arrangements. A personal swarm of 'Ufog' would be a most useful, multipurpose tool! (And in time, as we approach the singularity, perhaps we will become the ufog...)
Even in your present biological form, Ufog could be used as the interface between you and the immediate environment. Like the artificial human in the movie "Virtuosity", your cloud of Ufog could harvest needed atoms and molecules from the matter it touches. Unseen by it's owner (or anyone else), the swarm of molecular sized Nanobots would import materials and repair your body and themselves. No need to eat or eliminate wastes either.... all import or export of material is accomplished transparently at the molecular level.
Utility Fog could virtually read your mind, and anticipate a course of action... with large arrays of molecular sized sensors. A physiological response related to joy would cause the fog to part.... allowing the hug of a friend. A fight or flight response would turn on security mode.... a grizzly couldn't touch you!
Damage repair would be immediate and complete: Nanobots both in and outside your body would heal almost any wound. But, Ufog would act as a shield before any damage was done! The outer layers of fog would harden strong as rock in fractions of a second, and the inner portion of the swarm would actively cushion your fragile body better than the best air bag. Of course, Ufog could repair itself... or sacrifice its' own material if necessary.
Jump off a cliff and your (hopefully large) mass of foglets extend from your body, adhering to the cliff wall to slow your fall to a pleasant decent. Jump from an airplane.... the fog expands into a very large parachute... you descend at any rate you want!
High bandwidth sensors and communications links would provide a profound and intimate interface between the environment, other linked minds, and you. See in the blackest night like Noon time, or view the enhanced reality of the inside of an object. (Remember the variable spectrum scanner the Alien had in Predator II?) See what your friends are doing 1000 miles away, while you talk to them. Glance at the ground and see a molecular analysis of the soil. Or... pick up an automobile like a toy ...or fly under water all day without coming up for air. Even take a nap while you are whisked to a remote destination.... with no sensation other than g forces.
Need an energy recharge for all those molecular machines? Energy harvest from light, heat, motion, or chemistry and efficient energy storage would provide constant power. When in contact with other Ufog swarms, energy and material transfers would be automatic, if needed. You would have no need to even be aware of many Ufog activities, unless you wanted.
Camouflage would be at least as good as looking through a pane of glass... ala' "Predator". See great distances with telescopic vision... or magnify and analyze microscopic objects. Need a tent/room for the night? Just lay down on a feather soft layer of foglets... while the outer layers of the swarm harden to protect you from the elements and harm. The fog could warm or cool you... no matter the climate. Privacy? The outer layers turn completely opaque, even to full spectral scans, but you could see out like it was clear (the reverse of camo mode) . And... maybe best of all....never get another mosquito bite!
The possibilities are virtually endless, and I want it NOW!
Nano-Nova.com March 2001