Bio-metrics are great if used appropriately and validated. We can use lots of identity methods from certificates to passwords. The biggest problem out there is that there are a number of people/nationalities who need an identity validated and verified who do not have documentation some countries may require - passports, birth certificates etc… Ok… we may need a device to create a biometric print - smartphone for example. To complement identity management we can append/amend the identity with validated access. For example if user A had an identity and had passed a driving test in Europe then the signature would contain said information you can go further - passport, credit check, employment background etc… Blockchain to me seems the ideal platform for in the UK as an example the government gateway id would be added to your signature then the appropriate information afterwards. The benefits would be huge !