Object identification options, reliability and cost...recommendation
Consider this chance: you can use NFC tags (it's becoming popular, and you can already buy stickers from China at a very low cost), and with a reader you can not only read the tag, but create a communication session with the TAG (identification, encryption, data transfer...).

Plus, since many vendors are embedding NFC readers on their smartphones (Samsung Galaxy Nexus has been the first), you can think of creating a smartphone app to replace your reader.

For the tags, gargoyling gives TagStand, IdentiveNFC and many others, with prices below 1€/tag for small numbers, you can go much lower with big purchases.

Reliability and security are surely available, as NFC is being used for payment in many places, and it's being adopted also for ATM services.