3M's Nexcare Reusable Hot and Cold Pack is probably the best item charged to us at the hospital because I can still use it at home, use it well, and really benefit from it.
It relieved my aching back from having to lie down for so long. It also helped ease my gas pains after my CS delivery. Then, when our neighbors in the OB ward were getting excited over the air-conditioning, it warmed my newborn to sleep. Now, I am using it to prep my breasts for breastfeeding and pumping.
Granted, we've only ever used Nexcare's Reusable Hot and Cold Pack as a hot pack but I really love it, really recommend it, and will certainly buy another one again. Perfect for when you strain muscles from using pull up bars or cooling down a feverish tot. It's really a better alternative to ice bags and hot water bottles.