eDNA is one of the more creepy things you can think of in a dystopian future e.g. you can engineer humans to require a specific synthetic amino acid that doesn’t appear in nature this is essentially a potential biological DRM.
While applying it to humans directly is unlikely applying it to be some sort of DRM for drugs to prevent generics from working is quite a realistic possibility.
Combine this with some sort of blockchain straight on your DNA, you could have a permission system to grant/deny access to things, that would work not only for your biological system, but with binding contracts on the real word. Like bad credit, or denying access to your bank account, to kill someone by making his system 'forget' how to process a given amino acid, or make them dependent of some drug to live so a government could just wait a "traitor" come to them so he/she can keep on living..
While applying it to humans directly is unlikely applying it to be some sort of DRM for drugs to prevent generics from working is quite a realistic possibility.