I have no idea if someone has picked up on this idea but as there is a proliferation of internet-accessible radio stations playing requests and places like You-tube storing video, this technology could be combined with the now traditional e-cards to become AV-cards (audio visual email post cards).

Simply select your background texture/ colour, embed your video and type a message or for an audio card - attach your message and select your personal photo or image to accompany it through cyberspace.

Yeah, I know there are other factors that could present a problem like ISP speed, computer age etc but there are always going to be these challenges.