A system and method configured for conducting a transaction between two parties using a mobile device, or a plurality of mobile devices. In various embodiments, a system for conducting a transaction can comprise an accessory device having an accessory device module and a hardware component, where the accessory device can have various accessory device capabilities. The system can further comprise a mobile device SDK incorporated into the client application and in communication with the accessory device, where the mobile device SDK includes an accessory conversion module in communication with the accessory device module and where the mobile device SDK provides data to the client application. The client application can request accessory device information and receive accessory device capabilities, and the transaction data for the transaction can be provided in a defined structure between the accessory device and the client application via the mobile device SDK.