If it doesn't work, you are doing it wrong – Sparge Pal Review

I saw several reviews blaming this app for inaccurate strike temps, but I have had 100% accurate results. Take your strike temp from the mash tun not the liquor tank. You have to adjust for the drop in temperature your equipment may cause. I go 10 degrees higher and after transfer the water is the correct temp or a degree too high (so I wait a few before dough in). I do not use the boil time feature.
Review by RDK70 on Sparge Pal.