You can conveniently monitor temp, ph, orp, salinity and o2 and also automate functions (lights, heaters, autotopoff, etc) with a decent controller (reefkeeper or apex). As always, the more money, the more is available.
Unfort there aren't probes for monitoring everything.. and some that are available are cost prohibitive. I'd think just monitoring temp and ph is adequate. When you have an up and stable system, just using test kits periodically is fine.
I should be getting an Apex this week. But you can't really go wrong with other makes. They all work very well and have their own avid fan base.