Neptune has a system as well but I’m not sure what it tests. Personally I don’t think it is worth the money for any of the automated systems. My pH is monitored by my Apex, only because the probe came with the system, and I rarely test the others. When I do, I use the salifert test kit for nitrate and SeaChem for ammonia. I hate API kits they are notoriously inaccurate. I have never owned a nitrite test kit. Personally I don’t worry about pH. There is no point in chasing it especially if you have no coral. Chasing pH can really mess things up.
I know seaChem has both a pH and ammonia badge that cost very little (~$10) and hang in the tank. They give real time readings. I’ve never used the pH one but I always use the ammonia badge in my QT tank. It works really well.
My current tank (A reef tank) has been up and running for over 5 years and I’ve had SW tanks for over 20 years. I attribute a lot of my success with my current tank to the fact that I don’t stress over parameters. I just let it run as it’s own tiny ecosystem. I do water changes and that’s about it. My stock level is appropriate for the tank size. So things stay stable. In the time I’ve been in this hobby I’ve had the more success with this approach than I did in the past where I chased parameters.