I wouldn't base so much emphasis on worn devices. Ok, if we can arrange for information to be delivered to a worn device, that's great, but maybe leveraging on existing devices (ie. PC at home) and infrastructure (ie. Internet for delivery) we will be getting to implementation a lot faster then with the "techno-gizmo of tomorrow"-approach.
Take for example the fact that many cards are swiped at the check-out cashier and the implementation effort (and cost) would be minimal if those cards conveyed an email address (or other drop-box distribution method) where the digital receipt of the purchases would be delivered to, naturally containing the GTIN codes of the products purchased.
This would be a form of Post check-out Consumerium that requires no additional hardware for the consumer, a simplification compared to Check-out Consumerium in which NFC (or Bluetooth) would be used to transmit the digital receipt to the consumers worn device, most likely a cell phone or PDA