Has Anybody Tried This Marketing/Advertising Idea??

My husband just forwarded me this pic of a cool idea for marketing/advertising. I have seen a lot of REALTORs or mortgage people (and other service industries) do the car magnet advertising--but not like this.

While I DO have car magnets, I have not advertised on my car quite like this. I also have a lot of business cards with magnetic backs that stick to magnetic things. I've never tried both together quite like this. Interesting concept. What do you think? Oh, forget the fact that REALTOR is a trademark and should either have the capital "R" circled OR the word should be all capitalized...

Also, if you HAVE done this, what has been your return on your investment? Or, if you don't keep track of those kind of things (and you SHOULD), what has been your experience in terms of generating new business/leads/referrals? Whether you are a real estate agent, mortgage person, inspector, or other service person, I'd be interested in your results.

Thanks in advance for replies. :)