Helmets with blood groups

None can deny the fact that helmets are life saving..
One more curious thought came to my mind today (while I was not listening to the boring software engineering lecture :p). Can we not have people to print theory blood group on their helmets ... this will server two utilities. Namely :
1. In case the person wearing the helmet meets with an unfortunate accident and is in need of blood, the blood group can be quickly known by looking on the helmet.
2. In case someone meets with an accident, and is in need of blood, he can readily get help from the person wearing the helmet; if their blood group matches.
On the final note: donate blood save life..