...
Basically when properly used the keys cant be stolen, transactions are restricted to the card owner; in other words the current issues of wallet theft would not be possible, that is without a rubber hose.
...
The reason I started this thread is I am curious how much interest there would be in something like this.
When per-account/transaction authentication is supported it would be nice to be able to use a smartcard or other trusted store (TPM, HSM, etc.) to launch the client (open encrypted wallet) and authorize transactions.
With the recent malware attacks on wallets themselves, attacking locally running bitcoind processes to make fraudulent transactions is sure to come next.
Multi-factor authentication and authorization as with smartcard systems you mention would be a convenient way to nullify this risk.