There are plenty of "discreet" medical ID bracelets. It all depends on what color and style you want to get one in.

Obvious answer your heart and your muscles need plenty of oxygen and if you don't have enough oxygen, your heart needs to work harder so you don't die.

Well if you already talk to him plenty, try to make it a little obvious so that you can tell him without totally shocking his brains out. Guys are dumb you have to be really super duper obvious for them and be patient if they still dont get it. Just hang out with him more and alone if possible and tell him.

This is just a guess but im going for Paris because their are the obvious ones like l'arc de triumph and effiel tower but their are plenty of other ones as well.

The adjective of "obvious" is "obvious."