Journal: Yates's Bar Chain ID Scanners

I was in Leicester Square, London, last night on my way into Yates's bar when my friend and I were asked for ID. We were told it was compulsory, but I didn't have any with me. My friend had his, and gave it to the bouncer. The bouncer then walked over the the wall near the entrance and put the card against some device, before giving it back. I asked the bouncer what it was, but all he could tell me was that it's a scanner. Has anyone seen this before? Is anyone aware of what information the scanner is collecting?