I dont know much about temp surfing, but for milk frothing, there is a standard type of thermometer that has a clip to attach to the side of a SS jug with a dial indicator. Ive seen them in 2 sizes.
I have 2 of the small ones. I think the larger ones are more geared towards cafe use.
I got mine at a Housewares shops for $10 each. Ive seen them priced up to $30 in some cases.