In my experience, the problems are a result of the manufactured constraints on the physical hardware/sensor devices. Mountings and power and connectivity. Receiving data from an array of devices into a shared storage system for analysis is a well solved problem. Receiving data from multiple sensors on a fixed interval, when the sensors may be made by different companies/work totally differently, is where the complexity lives. Combined with each company trying to build their own awful closed source proprietary data system on top of their sensors, you've got a really terrible time.
> SQL turns out to be really slow for this kind of data
I think this is just poor modeling. SQL is just fine for the work you're talking about.