I use an app for my android phone called Brewzor. It has some stuff to work with beersmith, but I really use it for all of the calculators. It has a strike water temperature calculator, IBU calculators, and all of that.
Remember that you need to preheat your cooler if you are using one, I usually heat my strike water up 3-5 degrees above the calculated temperature. When I add it to the cold cooler, I give it a couple minutes, and it is right at the proper strike temperature. I then add my grain, and I am right at my proper rest temperature.