The coolant temperature gauge is pretty accurate, at least on my Gen 2.
I use a Trail Tech TTO temperature gauge (Trail Tech || TTO Temp Meter
) to read the oil temperature at the test port and the coolant temperature at my Thermobob 3. Both are left over from doing oil testing on the PDW mods and from doing coolant temperature testing for the T-Bob 3. I have two sensors and a switch going to one gauge.
For ambient air temperature I use a stick-on thermometer designed for reptile cages. The typical stick-on car thermometer that you put in your clapped out '71 Vega is ridiculous; they read from -20F to 140F. The range of interest is so compressed you can't read it. For much of the thermometer's range you'd either be dead or wishing you were.
"Reptiles pretty much like the same temperatures we like to ride in, and the thermometer reflects that", Tom said hotly.
The reptile thermometer (
) reads from 20F to 120F; I've ridden in temps ranging from 25F to 115F, so it seems reasonable. It's also big enough to read easily. They make them big because many reptile owners are former Pro Wrestlers (they like to wear snakes around their necks). Pro Wrestling is real and they get beat up pretty badly, getting hit with folding chairs and whatnot, and they can't see too well.
I have a Jegs oil pressure gauge connected to the cam banjo, in parallel with a Ninja pressure sensor, both courtesy of Paul (pdwestman). I don't recommend that you install either to the cam area unless you like to be frightened or unless you have done his mods to the oil system. Put a port in the filter cap. Easy to cheaply undo.
I used to have one of those strip gauges (http://www.ebay.com/itm/LED-Auto-Car...-/121160176396
) that did ambient temp, voltage, and time. It kept getting filled up with water, so I ditched it. I no longer care what time it is. The sun is up or it ain't, so it's either daytime or nighttime.