I am very suspicious of this for several reasons:

• It is an unverified chain mail, and I'm still waiting for Bill Gates to give me money for using the internet.
• There is no mention of it on any authoritative crime information sources (e.g. the SAPS).
• It's a silly idea:
• You don't need technology to locate random people, you can find them in their houses, offices and cars. I say 'random people' because:
• They don't seem to be targeting wealthy people, two people in my office (one driving and Uno, the other a Getz) have received one. These cars would not indicate them as wealthy.
• They are handing these out to lots of people.
• Correlating which tag belongs to which mark and why is a significant amount of effort compared to just following their car. Additionally, following the car would allow attackers to judge when to attack, these locators would not indicate opportunity very well.
• They are too small to include a reasonably priced GPS & communications unit, and hi-tech spy gadgetry would make the criminal's ROI pretty poor. They could have some for of radio beacon, but that would require them to drive around until they 'found' a signal and home in on it. This is okay if you are tracking one or two people, but not thousands.
• They are actually branded with Caltex's current 'Diesel Power' campaign advertising their low sulphur environmentally friendly diesel. It would make sense for these to be solar powered to advertise the 'environmentally friendliness'.

I think it is far more likely that this is the usual chain mail rubbish we usually see. Alternatively, it could be a clever way for a competitor to trash Caltex's campaign.

This isn't authoritative, just my thoughts, it could in fact be a campaign from a dumb criminal, or involve some kind of high-techery I am not yet aware of.