how can we realistically protect something we broadcast.

With appropriate privacy laws and security measures. A smartphone is publicly broadcasting information, in that any other person could receive the radio transmissions emitted from them. But such eavesdropping would be illegal in most cases, and is mostly encrypted to hinder bad actors who don’t obey such laws.

It’s important we act now to ensure there are suitable privacy provisions in place now for all biometrics, before such things as mass DNA collection and sequencing are practical. Once such technology is available, perhaps we will also have to adapt our behaviour in public to prevent leakage of unprotected biometric assets.

Time to start advocating for biometric privacy, and investing in bodysuits and hair nets.