Niko said:
"Imagine chemotherapy, except that the poisonous chemicals ONLY attach themselves to cancerous cells and doesn't kill healthy cells, and then those cancer cells are trackable and detectable while being specifically targeted by the medicine"
dude that's freaking awesome!!
Word. It definitely is. It's a great idea, and it's gaining some ground. One of the ideas out there, which is one I've heard about since a professor at my undergrad university was working on this, it to make a custom RNA or DNA molecule, like for instance making square. They can do this since they have specific reactions that will form RNA of a specific shape, like a reaction that will make a strand with a 90degree bend in it and another reaction that hooks strands together in a way that it will some out a square and not a long chain. With a square, then you can use reactions to attach different things to the corners: a drug to one corner, a tracer chemical to allow them to see it in the body like those radioactive dyes, and on another corner a specific type of protein or functional group that will attach itself to problem cells like cancer or what have you to deliver the drug. Instead of carpet bombing your entire body in hopes of killing those few cancer cells, you're shooting in some precision-guided munitions with few to no friendly-cell casualties. Awesome stuff. Not on the market or likely anytime in the next decade, but it's something in the pipeline. Who knows when it'll happen, but hopefully someday.
OP-
If it has to be something on the market now, then you're kind of limited because most everything out there is still "what if" and "how do we", few things are commercial so far. Seriously though, computer processors ala Intel passed into nanotechnology land years ago, and these new realms have revolutionized life on earth through better, cheaper computing. I don't remember off the top of my head when processors crossed that 100nm barrier, but it is close in the time when computers really became a staple of everyone in the western world and became completely necessary to modern life like never before.
As far as an invention that relies completely on nanotechnology in stead of just being improved to new levels by it, well, laser diodes and LEDs are certainly of interest to you if you're here. Laser diodes don't really work at larger scales, so nanotechnology is essential to them working like they do now. So there you've got all CD, DVD, Blu-Ray/HD-DVD, and the entire backbone of the telecommunications industry, including the internet. Fiber optic cables are the backbone of the world's communications infrastructure, and wouldn't work without lasers. Without lasers, we'd be watching VHS tapes while waiting for our 56K modems to dial in or download those tiny images that were the most it could handle.