Sony and Validian have come up with what i consider the first cool use of PKI. a fingerprint reading USB stick with a self-contained IM client. you can plug this into any computer anywhere (no drivers needed on most modern machines) and have secure conversations with anyone. unplug and the computer has no record of the conversation (assuming there aren't any keyloggers, etc)
very cool.
sure, one can use the PKI feature in addition to the Validian Flash Communicator, to secure his conversations, but the Flash Communicator itself provides secure exchange of messages and files from anywhere to anywhere over the Internet. Files can be of any length and any type, including video, audio, images, software. Plus both parties are authenticated before exchanges can be made, so it prevents SPAM and rogue users.