Signing in to a lecture with a smartphone?

Does anyone know of a way setting up a classroom or lecture theatre to allow signing in to a lecture using a smartphone or tablet? There are several apps I have found which allow the teacher / lecturer to take a register using a smartphone or tablet, but they all seem to be basic specialised databases that mimic paper registers, with the person in charge still calling out names or knowing the attendees. What I am looking for is a means whereby the people attending can sign in electronically from their devices. Ideally, by a non-contact connection to a laptop or other device in the same room, rather than through a web interface. The purpose is to enable fast registration taking in a class of a couple of hundred university students.