Hey Bjarney,
When it got real cold here last year and I was on holiday,I threw a few short lengths of 20W heat trace into my shoes and wore them around outside.
Magic I say, even though I had to run them on 230V and carry the flex as I walked.
Imagine 12/24V electric boots with an inter-woven heating element!.
Don't tell me someone has already had this idea!. [Linked Image]