the acjr comes with a ph probe. it also comes with its own power strip and is able to control each individual socket on the strip (i have an 8 socket strip).
you can program the acjr to turn on/off the power to the socket your "kalk device" is plugged into based on what your ph is reading. its a simple code...if ph>8.26 then device on/off etc...the acjr does powerheads too, random flow, alternating back and forth...light control, sunrise/sunset, good piece of equipment.
i use a litermeter3 dosing pump, when the ph reaches 8.26, during mid-day, the acjr kills the power to the socket the doser is plugged into. when the ph goes down, in the evening, the acjr turns the power back on and it continues its dosing of kalk.
the trick setup is to have two top off units pulling RO/DI from one source.
unit one is the litermeter3 dosing kalk from a kalk reactor and dosing randys two part...the LM3 can control 3 pumps. unit two is any off the shelf ATO device. the idea behind the second unit is that you want to continue topping off even after your kalk doser has been shut down. you are trying to avoid any salinity swings here...
thats just one way of skinning a cat...there are many others.