Flutterby™! :

Via Uncle Aussie comes this article about transmitting clandestine messages in DNA. It also uses some marker information so the actual message is buried in huge amounts of noise, which is good to keep crypto attacks less effective.

The researchers proved the DNA microdot works by pasting the tiny dots over the full stops in a typed letter, posting it and then analysing the dots when it arrived back. The message was received, loud and clear.