I'm looking for a very good foot spa. It must heat up cold water. Most,
if not all, of the foot spa's I've seen do not heat up water. They keep
warm water warm. I do not want any of these foot spa's. Please only
ones that truely heat up water.

It might be helpful to the question at hand if you could indicate
where you are in the world and how far you are willing to travel for
this service?

You might give this one a look:

http://www.amazon.com/exec/obidos/tg/detail/-/B0002AIVFY

I've got the same question and looked it up for hours. 
The only thing I've found was:
(actually I've seen several pages on the same product)

http://www.folica.com/HotSpa_Foot_Bat_r1520_1.html

This appliance is claimed to be able to heat cold water and
some user reviews are affirmative on that. Hope google researchers
might find a better answer.

From Amazon:

http://www.amazon.com/exec/obidos/tg/detail/-/B0006PS45C