Perhaps there is affordable equipment good enough that if there was a deivce at every feed location, or at least some of them, it could in a way triangulate. On a really large layout there will be multipel power sources as well, with insulated gaps between sections on different power sources. Now, if each section were trivial enough, one of these devices in each section could work for that section and not interfere with the one in the next section.
With this you are quickly approaching the currently common method of using occupancy blocks, for which electronics are quite simple and not too expensive ($30-$40 for a device capable of monitoring 16 blocks).
Well, I already belong to one club. I know some of the others around the area. I know some custom layout designers, but I don;t personally know any of the few layout builders around.
Would be something to think about for retirements, I;m not really looking for a major career move at this point, not to mention there's no way designing and building the electronics for custom model railroads could ever pay what I make now in my IT consultant job.
Tell me about it! I'm in the middle of designing and building a custom control system for an acquaintance and there is no way I can charge him anything near what would be a reasonable wage. I'll cover the cost of material, and be left with enough for a kebab. Yeah, yeah, I'm selling myself low, I know, but building stuff for individuals is not going to bring the bacon home, unless you can find yourself a benefactor who will finance your hobby. On the other hand, we've had a couple of nice commissions for architectural models (not train related), and those were decent contracts. Of course, the customers in those cases were not individuals, but ultimately government facilities. Those guys have the $$$ so they'll pay pretty much whatever you ask, because the market is so small you effectively have a monopoly.
Now if someone could hook me up with Sir Rod Stewart - although he already has a couple of guys to help with the wiring on his layout, and he lives on the opposite side of the US as I do. Yes, THAT Rod Stewart - he remarked that being on the cover of Model Railroader magazine was a bigger thrill than being on the cover of Rolling Stone. He has a beautiful US style layout in his LA home. Supposedly an equally nice British prototype layout in his London home.
About two years ago he was in Zagreb, so we invited him to come visit our layout, but unfortunately he did his concert and immediately flew to the next place.