Very, very interesting. Still a LONG way from being proven, but huge potential.
Antibodies are molecules that (among other things) glom onto things to muck up the operation of pathogens - like things that make it more difficult for SARS-CoV-2 to attach to cell membranes, that sort of thing.
Nanobodies are even smaller molecules that do something similar. Researchers have developed one that, in a vial in the lab, seems to neutralize SARS-CoV-2 even better than human antibodies. It's extremely powerful and stable. It can even be powdered for delivery through inhalation.
BUT...it hasn't been tested even in animals, yet alone humans. We don't know if it works. We don't know if it's safe. They're just starting to plan all that work. If it comes together, this could be a simple inhaled drug that protects against COVID-19 infection. My guess is this is probably a year out if things go well, but still good to know of another tool in development.