Info 2 sd card protection

Hi to all

after going thru all relevant pages about this I could not find solution.

I wish to password protect sd card in my phone. I have Sony Xperia neo with latest official rom and option for sd card encryption is missing. Now I know that there are programs to encrypt specific folders but that to my knowledge is not transparent to system and requires me to decrypt each file before use. I had older phones (nokia and palm) that could set sd card password and remember it but sd card was useless on other device, or if original device was reseted to factory defaults.

Any idea on how to address this problem? I find it interesting that this simple option is missing from such advanced os as android is.