What system parameters would be interesting to observe while driving?

I'm using
Car Scanner ELM OBD2 which lets me build a digital dash from hundreds of possible sensors.

 

Amps going into and out of the pack and voltage difference between blocks in the pack. The higher the amps, the greater the voltage difference. And Dr. Prius app provides this data and more all on the same screen.

 

Using an app you selected?

I wonder what its value labeled "oil temp" really is.

 

zero value

 

There never has been one in the engine, at least through Prius gen 3. Whether one could have been added for gen 4 or 5, I don't directly know. The wiring diagram would answer that question.

There have been apps reporting an "oil temp", I think even for generations we know have no engine oil temp sensor, so that invites a question what is really being shown there.

It could be a transmission oil temperature (gen 3 has such a sensor). It could be some other PID that somehow got the wrong name in the app. Or it could even be reading some bytes out of an ECU response that don't represent a known PID at all.

I feel like I recently saw a thread with a photo of a display showing "engine coolant temp" and "engine oil temp" and the numbers were substantially different, which seemed like another reason to wonder.

 

As your battery pack gets older after a decade or more its essential information.

 

If you're driving in the mountains, maybe engine coolant temperature.

 

Both engine coolant temperatures with user settable audible alarms. An indication before its too late with an audible so you don't have to watch it.