How -To:
All I have is quick fingers and some spare time - I've literally typed in 500 reference numbers and recorded the results. Since "Not Recognised" and "Decided" status does not change at all, the tracking is only needed for "Awaiting Decision" and "Open". In my particular case it's now only 73 (out of 500) lookups - it doesn't take longer than 10 minutes.
I wouldn't worry about overloading the system with a script for mass lookups as this is an offline status storage and not a transactional database (the queries are not being passed to the actual source system - the response is way too quick). There could be an IDS/IPS system that may react to a large number of requests coming from a single system but 500 or 1000 is not really a large number especially when spread out over few minutes - purposful delays can be programmed such as 1 enquiry every 300ms. Knowing how the government operates and lenght of it's change management process, I seriously doubt a captcha will be implemented any time soon unless it was already on the roadmap 2 years ago

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Usefulness:
It is quite useful for me as it shows that cases around mine are being progressed. Only very few other cases than naturalisation and registration are being considered for such a long time. So if a status changes from Awaiting Decision to Decided nearly 6 months after the application was registered, a large proportion have to be the cases similar to mine and not the "1-day turnaround premium ILR" etc.
Now, all I'm getting out of it is comfort that similar cases around my number are being still "Awaiting Decision" and they are progressively getting the "Decided" status.
There is a big difference between precise measurements and just an indicator - I'm fine with the latter. When I look at the forum topics with timelines per month, it feels like nearly everyone in May, June and July got their cases decided, while mine is still outstanding (forgotten, stuck). However when I look at my statistics, I know that a good quarter of the people still awaits. Or even more if other types of cases are also included in the same refrence numbering scheme. That gives me certainly more peace of mind...