My elderly mother, borderline for dementia diagnosis, used to use hot water bottles to help an ache in her lower back. Pouring boiling water into a hot water bottle and doing the cap up properly became too dangerous, so we switched her to using wheat bags that go in the microwave for a minute or 90 seconds. That worked well for a year or so. Then she overcooked a wheat bag. Thankfully, only a little too much which caused a nasty smell but nothing worse. Then a month later (yesterday) she did it again with a replacement wheat bag, but this time the Fire Brigade were required. No more wheat bags.

Can anybody suggest something reusable that can be used to provide localised warming, ideally whilst seated, that is safer than hot water bottles and wheat bags please?