I just picked up he new Red Sea Reef Foundation Pro test kit. They sell a combo Ca, KH and Mag test kit. I got mine at PureReef for about $45 after ARC discount. I bought this because I have heard they are very accurate. Red Sea makes D&D Test kits, so that should hopefully speak to their quality as well. I'm using it as a double check against my Saliferts, but if they are accurate I may use them exclusively.
I checked the Salifert KH Reference solution with the Salifert and the Red Sea KH kits, and the Red Sea was actually closer to the Salifert reference KH than the Salifert was!