Hum, I trust a cheap gauge about as far as I can throw it, and I SUCK at baseball.
Cheap gauges are cheap for a reason, their ability to repeat and to be accurate is highly suspect.
If you're going to spend some money on a tool at least buy one that you can have some confidence in. Have a look at those offered by
mcmaster.com
P/N 4129K12 is a glow in the dark faced pocket sized dial thermometer for $9.69 Accuracy is +/- 2* with a 0*-220* range.
P/N 3989K7 is $32.77 for a 6" stem length. It is made for perm install if desired. Uses 1/4" NPT threads. Accuracy is +/- 2.5* for the 0*-250* version.
P/N 3982K11 is a pretty cool magnetic surface temperature gauge for $35.76 Doesn't need a magnetic surface to work, just to stay in place. Accuracy is +/- 5* for the 0*-250* range version.
Try finding accuracy ratings for any cheap gauge, or for that matter for any of the typical automotive gauges.
I'd rather have some high quality warning lights than a bunch of gauges. I'm sure that puts me in the minority. That's OK, I'm used to it here.

I know "idiot lights" got their name for a reason, but the truth is that you are far more likely to quickly notice a light than a gauge reading something it shouldn't. There are probably guys who can beat a light to detecting a problem, but not everyone can - All of the time. Most of the big names in gauges also make temp and pressure switches that you can buy in a range of known set points (unlike most OE lights). Since the switches only need to one discrete thing they are far more consistent and accurate than a gauge sender.