london underground give out badges to pregnant women with 'Baby on board!' written on them to draw your attention to the fact that they are pregnant and may want to sit down. now i'm all for pregnancy but i've come up with some alternatives for more trivial reasons people might want to sit down. i too have made full use of the 'exclamation mark of urgency' utilised by tfl.
i'm selling them as badges and/or stickers, get in touch if you're interested.