Which Wallet clients support a universal export .wallet file? Is there a universal export format for wallet clients where users can use in multiple programs?

What are the list of clients/apps/programs that support this format?

I want to be able to export my wallets to my other programs for a piece of mind. I'm particularly looking for cross compatibility for Android, Windows, and Mac.
There are a few different types of files which all contain the same basic information, an encrypted copy of private keys. In short there is no universal format yet.


The satoshi client uses a wallet.dat file, but as far as I know only
armory supports that format.
Blockchain.info and use uses an encrypted json file (wallet.aes.json)
Multibit uses a .wallet format which I believe is unencrypted.
Multibit also has the ability to import encrypted json files for
private keys (i.e. from Blockhain's backups)    
Electrum uses a   .electrum file, but you can import and dump private    keys using
command line functionality.


It would seem that the easiest and most universal format for now would be an aes encrypted json file for exporting private keys.