If an ambulance is called or you go to hospital your parents (or if you are over 18 your emergency contact which is usually spouse or parents) will be notified regardless.
Suicide watch is when you are committed against your will to a mental health hospital. They will keep you for up to 72 hours. The one near me has maximum security down to minimum security. Max security is where you start, and yes it is just like prison (just more freaks). Minimum security is like a bad school camp (minus the friends and fun).
If you tried to commit suicide via overdose, you will be forced to drink charcoal (which is incredibly difficult to do), if you can't drink it, a tube will be put down your nose and it will be poured straight in. Once you are sent to max security you will be stripped of all your possessions, jewellery, underwear and any cords in your pants will be removed. If you're a girl you cannot wear a bra, and wedding rings and any other piercings are out of the question.
You will then begin the hangover from hell. Your body will ache, you will have massive headaches, you will spew, and you'll be crapping liquid charcoal for at least 24 hours. You have to request cups of water, and you are not allowed any painkillers for the headaches. You are not allowed to sleep it off either, as you will have multiple visits with psychologists, and you will be forced to eat with the other 'inmates'. The food will make airline meals seem 5 star. And if you enjoy eating healthy food, too bad. Fatty food with little protein keeps the patients sluggish and easier to manage.
I really don't recommend it.