@ptmuldoon I agree, it would be a fun experiment to break down overall consumption of multiple devices but from a practical standpoint, just get two modules and be done with it 
Regarding the toaster: First it’s not a problem to detect states as long as they are characterized by a certain wattage (and/or duration). @binderth is right that it could be problematic to observe the toaster, as he will be active only for a short time. However you (@binderth) forgot, that most modules have a threshold option They will send acyclic extra measurements if a certain value is passed.
Both the mentioned Homematic and Sonoff Pow module provide this functionality.
I’d also recommend the Sonoff Pow as a cheap good module: