Other than an incident I read about involving a Jennings J9, I've never heard of an AD / ND with a firearm that is not being handled. As others have said, if the trigger is not activated, the gun will not go off. Simple. Of course, a manual safety will add to the security when handled, but really isn't needed when the firearm is at proper rest.
As for the awesomeness of Glocks, (and I know I'll get flamed for this, but....),in a nutshell....kb!!! (That's short for kaboom, for those not in the know). And yes, I have had it happen. Once, but that is enough to make you leary. (It's tough to finish firearms qualifications ducking behind your support hand every time you press the trigger). Before the attacks and assumptions come roaring along, understand that this particular Glock Model 22 had been inspected by one of our department Glock armorers exactly 7 rounds before the catastrophic case failure. And, no, the round count was not exceedingly high, especially for such a vaunted weapon self-proclaimed as the epitome of perfection. I carry a Glock as a duty weapon, but the only reason I do is the state bought it and they pay me to carry it.
Anyone still interested can check out this link: The Gun Zone's Glock Pages
And, just in case this hasn't been posted already, check out this article on a worn holster / firearm design combination gone bad:
Gun Accidentally Discharges (8 pics) That's not a knock on Glocks, just a reminder to buy quality equipment, and watch for wear issues.
Well, gotta go for now. I see flames and arrows on the horizon. Stay safe.
Life Member NRA
CCW / Firearms Instructor
Happily annoying Liberals since 1976.