I actually don't have any experience with controllers, I'm just in the shopping process as I've just reccently started to grasp the value.
That RKL does look really nice for the $. $99 plus the cost of a PH probe and you'd have your PH monitor/controller, temp, 4 controllable outlets, and plenty of room to expand from there. That would be cheaper than a PH monitor and 4 ditital timers, but it would do a whole lot more.
Also IIRC there have been a couple of controllers being sold reccently used for cheap. (RayD maybe?)
I think i was told to control or monitor PH you need to get more then the probe. I think you need this as well
http://www.premiumaquatics.com/Merc...Code=RK-30-0015-001&Category_Code=digitalaqua