That is the best idea I have seen in a long time... I think I will be getting my niece and nephew one of those signs for when their child is born in couple of months, though I believe I will make the sign a bit bigger because we all know someone will claim "Oh I didn't see that sign", then continue on doing it anyway... ~face palms~
I usually smile and talk to the baby from at least two people distance, while talking to mom or dad about how old they are, and how they are faring with the little one...