The better question is, does it actually matter? If this is a marketing ploy then we can just assume that its an attention grabber. For all we know, it could be a PRNG that increments when it feels like it.
I went to iguatemi shopping in sao paulo to test this stuff, it it apparently work, there's no rocket science behind it, because, you're not allowed to take those pieces from the hanger since they are a simple "thermometer".
