I use a heated underblanket, and it adds a touch of luxury to the treatment, most clients comment on it.
I also have a wheatbag in my towel cabi, its covered with a flannel that I sewed up and fits like a sleeve. I sometimes place this by the clients feet, on one of my treatments, I place it on the solar plexus.
the heatbag can also be placed under the neck or under the lower back.
I also have hand size wheatbags, and I sometimes give these to clients to hold.
Hot stones are also brilliant for adding a touch of class, I pop stones into a dry mitt and give that to the client to hold.