I check my salinity with a hydrometer I ordered from china. It was cheap and is really easy to use.
I have the apex controller and love it. The controllers are a bit pricey, but since I was just getting the system set up, and figured I'd have one eventually, I just went for it and got the apex.
I think it was a great call, as all the electrical, kalk drips, etc. are now built around the controller. The programmable outlets are sweet. If you get it and need programming help, let me know.
I only very periodically check tank salinity. I check it for my water change water, but with a top off on my tank, the tank just holds steady. pH and temp probes are great though (both come with the apex.) Heaters obviously on the temp probe, but if temp gets a half degree above set temp, fans turn on, 2 deg above set temp, MH's shut off for 30 min then re-evaluate, etc.
Have kalk dripping at night if the pH probe conditions are bet (on the hour between 9 pm and 6 am, if pH is less than 8.15, drip for 1 minute.)
Anyway, I love the apex.