In reality no tracker app can give you correct estimate of when your case is going to be decided. There's way too many variables for that and too much human factor. USCIS often changes priorities, speeding up processing some cases and slowing down others. Plus each case is unique. My friend submitted petition 2 weeks later than me but got approved about 5 months earlier. Both cases went to the same service center. We have pretty much the same story as to how and when we entered the US. We live in the same city, same nationality, about same age, same occupation. In my opinion these apps are not worth paying for. There are free ones plus websites showing stats for hundreds of cases - those may be somewhat useful.