This is one of the strangest satnav accessories that I’ve come across. Its makers claim that “tell-tale sucker marks on windscreens” are one of the major reasons for satnav theft.
So they’ve come up with the Nav-Mat, which basically looks like a beanbag for your satnav. It sits on the dashboard, therefore preventing those “tell-tale sucker marks”. Apparently “the contoured and weighted, anti-skid underside stops the device from sliding and, unlike traditional window mountings, leaves no suction marks on the windscreen”.
It’s available here for a bargain £19.99 (plus £5 p&p). Alternatively, buy some window wipes here for 99p.