Personally, I try not to overcomplicate things and rely too much on my own gut feel. Too much emotion = not enough rationality, but it saves me time in inputting data into a spreadsheet with formulas dictating how I make a decision. A personal thing, definitely, I can see how something of this nature would totally be useful.
I do keep keep track of SC earn to hit Qantas status throughout the year, but this is usually in a quick google doc, nothing special or automatic about it.
The only tool I do use to research status a little more quickly than what Qantas offer is mileage monkey - http://slfft.org - although with the recent changes to SC earn on partners, it's become less and less useful. To get Qantas SC (for full Economy earn) for multi-leg trips it's fast to use the 'Oneworld Explorer Validator' section, input the route (e.g. 'SYD-LAX-JFK') and then check the box to ignore errors, and the table in the results at the foot of the page will output a nice list of Economy, Business and First SC's earned if flying QF. It used to work for oneworld partners too, but of course they have culled the SC earn on oneworld partners on many routes, so now need to bear that in mind and calculate differently.
In summary... yes, it's hard to keep track of enough to plan for, so I've not bothered and do it quite simply.