I think this is the epitome of a "one-of" card. It's effectively a "First Aid" for a Hero, and it gives them a higher cap of health. Being able to put it on someone else is just icing on the cake. Low & high health Heroes alike benefit from this card.
Play under any player's control. Max 1 per player.
You get +3 hit points.
This is a solid vanilla card that I think is worth the cost, and if you are playing with multiple people, then adding a couple in allows you to see yours earlier if you need it and hand one out to someone else to make them feel safer as well. It could mean another round in their hero form they wouldn't have been able to do otherwise and of course you now have a new health cap.
When you play it, do you get to add the +3 hp right away or it only raises your maximum? Also, if you are at 2 hp and you lose this card, is your character considered having 2 hp left or he goes to 0 hp?