Piwoslaw -
I like the idea, but like others said, it could be taken the wrong way. This idea reminds me of the Meter Fairy :
I saw a much funnier version of the meter fairy on jackass :
Watch Jackass Video meter fairy from jackass season 2 Online | Browse Categories | jackassworld
It's actually illegal to be a meter fairy, at least in the jackass city (Oregon I think)! I've been thinking of making a "flat tire sign" for when I see cars with low tire pressure. Sometimes it's hard to roll down windows and tell them, so a sign would be better.
CarloSW2