Short-range wireless

Short-range wireless options for conveying the data at point of purchase relevant to the product purchase decision are:

• WiFi, a higher-overhead IP based standard (technically 802.11 and 802.11b and 802.11g) useful only if the hand or shelf device is IP-based, which requires at least the bulk of a wristwatch.
• Bluetooth, a digital standard for on-body devices at very short range, probably used for the communication between barcode scanner on the hand (a barcode scanner ring) and a wearable computer or other device dedicated to this need and kept in-store (unlikely)
• DECT, like Bluetooth, part of the IMT-2000 ITU standards
• packet radio, using FM subbands to broadcast information relevant to the products of concern - those in any given aisle for instance. This too is likely to require cooperation from the store that stocks the goods, which by definition will not be stocking anything they consider to be offensive - and thus will not be conveying negative information.
• FM radio, conveying voice briefings on each of the products, perhaps in a rotation, so tuning into that band with a common portable FM radio in the store, will inform you about the buying criteria (a lot less personalized, but more like standard media with no non-standard device requirements)
• shortwave radio, with desperate peasants and peons in the oppressed country where the goods are extracted and who are paid a pittance, trying to reach you on the band you are listening to on your shortwave Walkman, at the moment of buying. This seems unlikely, but, it's the only solution that would really be under control of producers...
• Near Field Communication
• RFID
• Smart Cards with embedded receivers