The most important thing with SI in hospital is let the staff know, but DONT SHOW OTHER PATIENCE. This can seriously trigger them, and they are here to recover. I unfortunately learned this the hard way, and disrupted someone's treatment. Please be very careful with this.

Also, try and focus on the fact that you're trying to get better, and SI - though feels good - is the opposite of getting better. Try and fight though the cravings as the result is only a temporary relief. Distract yourself with something that you can't hurt yourself. Charcoal or pastille drawings, playdo (my favourite), ice or cold packs, crochet. The staff at the hospital should have safe distractions like those. Maybe not the playdo... that's a personal thing for me.

Whenever I've been in hospital, except for one specific program that wasn't really "in hospital" we weren't aloud our phones, and they had a central computer in the common room. Some people were aloud headphones till curfew, as well as knitting needles and some sharps on some wards till curfew, but cigarettes and lighters or anything like that was locked up and you could only get them when you were off the ward.