(phew, what a title...)
Just got back from a couple of days in London, during which I made a quick stop in Westminster on the Tube.
On the way out of the station, one of the boxed/framed posters had a mostly grey background, with a small picture and a note that switching the bluetooth on your phone on would reveal "a secret".
Most people would probably never bother, myself on the other hand... I switched on my bluetooth, connected to the 'secret', and it came up with "enter password". Well that's a rubbish start.
I entered the usual default code of 0000 - - - - - - wrong password.
Tried again, but used the other default of 1234 - - - right password (it appears) - - - - - - failed.
And again - - - - - - failed.
So. What was an intriguing idea, which got me to stand there like a loon in a tube walkway; has ended with complete disaster. No ad received, no message, and it wasted several minutes of my time; not a way to make me buy something or feel positive about a brand.
I mean look, I was setting out intentionally to discover what the company and message was, and I cannot tell you either. I imagine it must work for some people, but any execution that can miss a large chunk of potential viewers just simply for not guessing the right password or having the right phone model... risky.
So the moral: The idea is great, but if the execution cannot match it, then it's simply a big waste.