I bought a pair of those grip heater plates,.. and sewed one onto the end of a scarf... it makes a little warm spot under my jacket, like a hot water bottle,(only less sloshy... and I don't have to bring it home cold)...
...
I have a buddy that rode to work all last winter with the heated grips... He said he couldn't have done it without them...
I didn't pay a lot of attention to the instal though...