Facebook mobile applications have a check-in facility that basically enables users to say “I am in a particular location” e.g. The Queen Victoria Market which, by the way, has over 18,000 check-ins so far.
Westfield have turned “Check-ins” into a marketing opportunity. When a user checks-in at a Westfield Shopping Centre they receive a special offer from that centre on Facebook. In the first week of their trial it is 30% of all full-priced jewellery at Angus & Coote Jewellers.
Not sure how widely available the technology is but it could have application to the QVM and General Merchandise Traders.