now heres another little thing i was looking at, a brush head that could dry the window after washing it, or may even suit traditional window cleaners, this brush head is called onesweep, add fan spray nozzles, and use as normal, it acts as a brush, but when you sweep or wipe, it clears everything in one go, also it hase a squeegie on it to. Even when wet the rubber bristles wont slide and cause friction on the glass
only about £4 each well worth a try,
http://www.amazon.co.uk/exec/obidos/ASIN/B0001PY4MY/026-5604240-5914838 
see it in action,
http://www.telebrands.com/international/onesweep.html