I want one. I've seen a nice pink one from Joules. But I want to know the point of them as opposed to putting on a jacket. If I am cold, then usually I would want my arms covered up too wouldn't I?
Someone please explain them to me. LOL
This thread is a little old, but if you’ve landed here looking for more info on heated jackets, we’ve recently updated our best heated gilet page with lots of great options, as rated and loved by Mumsnet users, plus info on how they work and whether they're the right choice for you. We hope it helps. 
MNHQ