When I travel, I really like looking at the public graphics for no parking, no entry, etc. Some places are basically just text, but others really have great little illustrations that communicate the message without needing words.

For example – I think it was in France or Spain where the No Trespassing sign is an angry little yelling man with his hand up. It would be helpful if more public graphic designs made this much effort.

Having something more personalized and hopefully less expensive / easier to bring with you sounds amazingly useful.