[zaarn]

Put a heat sink on the outside and a water cycle on the inside of the pump.

If you want to cool, you pump heat outside by stopping the water cycle when the material is cold, thus allowing the water to dump it's heat into it.

If you want to heat, you pump heat inside by stopping the water cycle when the material is hot, thus allowing the water to absorb the heat from the material.

You can increase the efficiency of this by having more water touch bot the inside and outside phases (increase material surface area in contact with water and increase surface area of water cycle heatsink).

If you want to allow sub-zero temperatures, add anti-freeze to the water.