I've wandered through the code and have seen how the temperature is collected and stored. Any plans to break it out? It'd be nice to have a proper timeseries store for those and the ability to add others- I assume many of us have environmental data- temperature, temperature again, power, fan speed, server stats, and it'd be nice to be able to write and read to a store from a plugin- such as for video overlays.
So I guess what I'm asking, it's come up, is it in your upcoming work?
It's something that's on the short list for 1.4.0.
If you have any specific implementation ideas with regards to a time series store I'd love to hear about them! 
Yeah, I read through it and got overwhelmed thinking about the possibilities. I'll do so again.
Is the short list published anywhere?
Not completely public but the results of last year's Patron survey and following prioritization are available on Patreon:
Tracking of other temperatures is basically this feature request:
As a metrics nerd, I'm definitely interested in something like this. I run my own graphite server at home and log all types of silly stuff, just because I can. On my octoprint system, I've added collectd as well as a couple home-grown scripts which submit metrics to Graphite, and I've used that to log room and enclosure temperatures with DS18B20 1-wire sensors. It's not native to octoprint, but it is a solution which allows me to get metrics into a TSDB. The one thing this misses is the hot end and printbed metrics, but if I really wanted that in a TSDB, I could enable the serial log and use collectd's tail plugin to gather and report the data without writing any code into Octoprint.
This would be very useful to me right now. I'm trying to find out why my prints fail mid print and I have changed almost the entire extruder.
Being able to monitor temperature would let me see if the heater is failing when the printer stops extruding.
@cmh good idea about the serial log, I activated it and I'm printing again now
I'd place my money on heat-creep, the heat from the hot end is creeping up into the cold end causing the filament to swell. Open a new topic as discussing it here is hijacking this thread.