Refractometer: Milwaukee Digital Seawater Refractometer
Calcium: Red Sea
Alkalinity: Red Sea
Magnesium: Red Sea
Nitrate: Red Sea
Phosphate: Red Sea
The Red Sea stuff is great, API will cost less and is OK in a pinch, but once you switch to RS you will ditch your API
Ammonia: Salifert
I have heard some good things about the Hanna Checker digital test but haven't made the leap yet, maybe someone will chime in who has experience with them.