We regularly attend/host a fair with business partners, mostly universities. We would like to be able to track attendance. Not wanting to depend on attendees having certain devices with certain scanner apps, we plan on reversing the process and supply attendees with printed tags/cards with a unique QR code (2D code). The idea being that they will then go to a room, have their card scanned, and we will know who went to which seminar. As there are 30+ exhibitors/partners, the scanning equipment at each stand should be priced below an iPad or a computer. Therefore, I would like to hear recommendations on a pen-shaped scanner that is able to scan and store. We would then afterwards 'empty' the pens - which should be marked of course.