Honestly, everything you mentioned are things you look at when trying to solve an issue with your rig. The main things I monitor are:
1) Coolant Temp
2) Transmission Temp
3) Charging Volts
Monitoring those 3 things while driving are going to keep you out of trouble. The analog needle gauge for engine coolant temp will not alert you to a problem as quick as your phone app will. By the time you see the needle rising on your dash gauge, your engine temp will have already spiked. Getting your rig pulled over and your engine shut down as quickly as possible can be the difference of replacing something simple like a radiator hose or warping a head and causing a major engine rebuild or replacement.
Most people don't monitor their automatic trans temp but they really should. Heat is the big killer of automatic transmissions and ignorance isn't bliss. The only thing Toyota afforded people with these rigs is an idiot light on the dash that illuminates at around 300 degrees. At that temp, your fluid is toast and you probably already did permanent damage to the internal components in your trans. When my trans temp is nearing 230-240 degrees, that's the point where I start thinking about pulling over and giving my trans a break and I did just that on a very sustained grade in Death Valley, California on a 100+ degree day.
Charging Volts is another big one, because just like running out of fuel, you can run out of battery volts. Once your alternator is charging subpar or not at all, you will be slowly draining your battery down. Once you can no longer power things like the ignition system, your rig will stop dead. So, knowing that you have a charging issue will let you know it's time to pull off at the next stop that has services so you can diagnose and fix whatever the problem is. Most likely an alternator replacement will get you back on the road safely.
Anyway, this is my two cents on the BIG 3 to monitor while you're driving.
