Can anyone direct me towards the best app, preferably free lol, that I can download to use my ipad or iPhone as a riggers control for my ion?

TouchOSC is about the least expensive decent remote for controlling the ion. You will need to get a layout for it and get UDP OSC up and working. If this is too technical for you then I suggest you stick with one of the more expensive apps as they are engineered to be easier to setup for the layperson. iRFR or oscRFR are both great choices for this although the oscRFR currently doesn't have layouts specifically for small screens.