This would have a lot of uses where you need to permanently or temporarily compare temps, humidity etc.... I would have many uses for it like water heater temp in and water heater temp out. Indoor and outdoor temp and humidity comparisons. Top of fridge and bottom of fridge as well as testing all the radiators for best performance (temp in - temp out should be about 12C).
So if it is possible to take multiple sensors and get the highest reading from the group of sensors for the highest value of the graph and the lowest reading from the group for the lowest figure, I think you can then do it. I have seen this done by other IoT 'brands' so it can't be difficult! (not for you anyway ).