You'll have to remember multiple UUIDs, one per service. Now that I think of it will be rather cumbersome. And bio data has to be editable if it will be usable

You'll have to remember multiple UUIDs, one per service. Now that I think of it will be rather cumbersome. And bio data has to be editable if it will be usable at all i.e. add/delete new entries - fingers, eyes etc. Damn, it is harder than it seems. Anyway, bio data as a login should be implemented, we only need to think exactly how.