The present invention provides a method and a device for piercing a body part and determining whether a sufficient volume of blood has been withdrawn. According to the method, a generic interface is exposed that includes a first method for requesting that a file be stored in a file vault. The agent communication indicates that a customer desires to perform a mobile wallet transaction using their third party mobile wallet. Power to operate the memory card through the second path, when not connected to a host, may also be provided through the external contacts by including a battery in the caps.