Mobile device payment system

A removable accessory for a mobile device for use in a mobile device payment system comprising:

• an external input interface for physically connecting the removable accessory to the mobile device;
• an accessory processor communicatively coupled via the external input interface to the mobile device for receiving data from the mobile device, the data including an account identification;
• a memory system accessible by the accessory processor, the memory system stores the data;
• a transceiver of the removable accessory communicatively coupled to the accessory processor for receiving instructions from the accessory processor and for communicating the account identification to a reader computer at a merchant location communicatively coupled to a merchant computer network system when the transceiver is in a vicinity of the reader computer;
• and
• a connection detection circuit of the removable accessory communicatively coupled with the accessory processor for automatically detecting the connection state of the removable accessory with respect to the mobile device, the accessory processor erasing the data in response to an indicator from the connection detection circuit that the removable accessory has been disconnected from the mobile device.

A method of making a payment using a mobile device removable accessory comprising:

• responsive to receiving a signal from a transceiver connected to a merchant computer system, the mobile device removable accessory checking its connection state with respect to a mobile device;
• responsive to the connection state indicating the removable accessory has not been disconnected from the mobile device since an initialization procedure had been performed, the removable accessory generating a transaction data set comprising a user account identification for a payment service account, an accessory identification, and an encrypted request identification for a transaction, and
• the removable accessory transmitting the transaction data set to the transceiver connected to the merchant computer network system;
• and
• responsive to the connection state indicating the removable accessory has been disconnected from the mobile device since the initialization procedure had been performed, transitioning the accessory to an inactive mode.