There is provided a mobile subscriber unit for a financial transaction token. The subscriber unit interfaces with a financial token or card that is in communication with the subscriber unit. The financial token or card has an onboard energy source so that the card token may operate away from proximity to a merchant terminal (e.g.; a POS terminal). In one implementation, the onboard power storage device includes a rechargeable battery or capacitor such as a thin-film capacitor that stores sufficient energy to power the subscriber unit's onboard electronics and/or the electronics of a financial token in communication with the subscriber unit. The subscriber unit may be a component of another consumer device such as a computing device, communications device, an item of clothing, an item of jewelry, a cell phone, a PDA, an identification card, a money holder, a wallet, a purse, a briefcase, or a personal organizer.