I use mine to control:
-my main light dawn/dusk ramp or aclimation color and intensity (Kessil A360we)
-Fuge light
-Auto Top off (bought the breakout box, $30-$40? Worth it) I use a high/low float switch setup, and also a float switch in my ATO container to remind me to refill it). I also have an ATO timer programmed so the ATO can only be on for 5 minutes maximum. IME on my tank the ATO should never be on that long. It will also warn me that the ATO was on for that long so I can check to see what happened...cord come unplugged, line clogged somehow, etc...
-Return Pump
-Powerhead
-Skimmer
-Heater
Now my control of my return pump, powerhead, skimmer are only on/off, but I am able to set up feed cycle timers. One timer stops the return pump and skimmer during feeding for 10 minutes. Another is a 60 minute timer for maintence that turns off all pumps, heaters, ATO, and turns my lights to full brightness (both tank and fuge lights).
I also have the autofeeder that feeds once per day. It is programmed so that the return pump, skimmer, heater and ato shut off for the duration of the feeding.
I have e-mail and text warnings if my sump level gets too high (ATO didn't shut off, return pump broken, any # of other problems), if the water gets too hot or cold, when my ATO container runs low, or if my PH goes wildly out of wack.
Even though I get these warnings there are also safety features in place. Ex: If the water gets too hot, it will shut off my lights in an attempt to cool the water, as well as cut power to the heater.
I plan on getting the salinity module to monitor my salinity in the future (which will also act as a safety feature on many things such as ato).
I sometimes travel on the weekends and with the apex I don't have to worry about the other thousands of dollars I've spent on my tank because I can monitor *most* everything right from my phone or computer.
Oh, I also have a webcam on my tank, so I can view both the sump and DT. Apex Fusion has a window for this, but to all my trying I cannot get it to work.
PS. I like my gadgets on my tank. The apex is just one more exciting gadget to play with.