The HealthVault platform and Microsoft Live ID do not support federated single sign-on, where a single authentication system can authenticate users to other systems.
There are two recommended alternatives:
Applications may use the HealthVault platform to authenticate their users and not have any application-specific set of credentials. This would mean replacing your current authentication system with the HealthVault one.
If historical or architectural constraints require an application to maintain its own credentials, then the app can use Offline Access to a user’s health record in order to avoid requiring the user to login to both the application and the Consumer Health Platform. Once this has happened, the user can login to the application and let the application interact with CHP without the user being authenticated there.