I also think that it would be super useful to see my temperatures in a graphic format. Given that there is nothing built-in, I was planning on downloading my data from Withings a few times per year and then generate the graphs. Unfortunately, the data Withings provides is garbage.
In your downloaded zip file, you will find a file called body_temperature.csv. You'll note a few things: (1) you get a nice date/time stamp down to the second (2) you get an INTEGER reading of temperature, supposedly in ºF (the header is labeled "value (°F)"). This, despite the app displaying to the nearest 10th of a degree. I went back through the app and collected the 173 data points I have collected since July to see what might be up.
If I plot the two of them on the same graph, this is what you get.
Do better Withings! This is just laziness and garbage.