Write down all of your passwords on a piece of paper and then retype them into the "memo pad" app on your IP4?
Don't mean to be snarky, but the password keeper app is proprietary to Blackberry and the data in the file is encrypted, I'm not sure you can 'export' it electronically.
What I have done is copy and paste each entry to an email but its tedious and then you'd still have to do the copy and paste after you sent each and everyone to your Iphone.
I have written all my info into a small book that I keep in a drawer somewhere .......
