For some reason this made me think that there's a lot of money out there for someone who designs/builds a hanging V window cleaning machine - just put the motors on the corners of the skyscraper and away you go!
Entrepreneurs - please give me credit 🙂

I did an internet search, and couldn't find a hanging V window cleaner, but I did find this, which is remote controlled and looks expensive-http://www.ipceagle.com/products/highrise%E2%84%A2-professional-window-cleaning-system#.WAfXemczXIU
A polargraph-type machine would be cheaper, I think, and, with the architectural drawings, or good photos of a building, it could be programmed - scrub, raise mop, move, mop again. I seriously think this is worth patenting, if it hasn't been already.
I think the fans on the one I linked to could actually have applications to our Polargraphs, because I currently have to tilt my frame in order to make good pen contact from top to bottom

I ordered one. I hope it works as well as it seems to in their videos. Once it shows up, I'll try to give my opinion on it.