Is it possible to find out how many virtual memory left free on iphone of my user?

Hey guys, my app is heavy on graphics and some time its peak up to 130mb of memory usage, so i got many complains about crashes on old devices. This kinda ruin my mood, because im test my app on 3gs ipod and if you dont run 5 apps simultaneously it works fine.

What i want to do is to check in my ini scene how much memory user have, and if it is not enough show a popup asking user to close other apps.
Can this be achieved in any way? Thanks.

Your app is not supposed to be aware of other apps, or the memory that they consume. You will almost certainly not get approved if you ask the user to close other apps. AFAIK no application on iOS does this even though it does sound the obvious thing to do. You might care to ask Apple if this behaviour is allowed.