I think seneye is utterly worthless for the price you pay. $220 + $10 month to measure what can be done for less than $20 for a whole year.
PAR measurement can be easily done for free or super cheap renting from your local reef club. That only really needs to be done each time you change lights and isn't really beneficial after that. Some say it's helpful to determine when a t5 or MH needs replacing soon, but those are so darn consistent, the Seneye is more likely to give you a false positive than for the bulb to die early or late.
Ammonia doesn't need to be measured outside of the random emergency or if you are one of those guys that thinks a cycle with fish is humane, then it only really needs measured during the cycle.
pH is useful to spot check, but continuous measurement is not important unless using in an aquarium controller automation like shutting off kalk or calcium reactor if the tank pH spikes out of range. The seneye can't integrate with any automation, so that parts worthless too.