A piece on Slashdot asks a question that seems pertinent to this site. What measures can be taken to prevent 'smash and grab' - from your car, when your valuable stuff is inside the car.
Aside from not keeping valuables in the car, obviously ;)
Apart from not keeping valuables in the car, the next best solution is:
Moreover, I'd say treat anything that isn't part of the car as a valuable. There are places where someone will smash and grab for 75 cents left sitting in the ashtray. Leave them no reason at all to target your car.
In my car, I lock small valuables in the glovebox. I toss jackets/clothing/shopping bags I'm not using in the locked trunk.
And, very important, I make sure no one is watching me as I put these things away. If you're seen, the whole operation becomes pointless because there's really only a difference of a few seconds between "smash and grab" and "smash, pop trunk/break glovebox, and grab".
I would go a little further. Don't just remove all valuables and all items that are not part of the car.
Remove all signs that something valuable might be in the car.
In summer 2010 some friends and I did a roadtrip from Budapest to the Romanian Black Sea coast. One morning at about 7am somebody smashed the window of the car as it was parked outside our hostel in Bucharest.
Nothing was taken. The glovebox was open. They broke into our car because they saw the mounting bracket for the GPS or the mark from where it normally sat (I can't remember which) and thought it might be stashed in the glovebox. So don't just remove your GPS, also remove the mounting bracket, and clean the windshield / dashboard so it doesn't even look like you might have one inside.
26 months on ... :-)
THe following is all via a link to one version of the supplied photo. There will be other related sites that use this image.
Related and useful - based on supplied photo:
The picture is used in various places on web.
Which links to:
Road safety and preventing smash & grab - relevant and good.
Window film ad useful for safety and slowing down attackers.