The last one I picked up had six probes and a Bluetooth app that went with it.
$36 new. The app was worthless, but 6 temp probes on the still were very helpful.
Cooling water in/out, ambient, exit air from radiator (air cooling the recirculated cooling water), head, and boiler temp.
But I’ve also used 4 probe sets purchased for $5 at the thrift store.
https://www.amazon.com/s?k=bluetooth+thermometer
@Beaker has a write up on thermocouples you should read if you’re at all concerned about safety. I would not use bare thermocouples in butane, but my understanding is they are considered intrinsically safe due to the voltages involved.
edit: Omega says I’m wrong. because the recorder/reader might turn out to be homicidal…
https://mx.omega.com/temperature/Z/pdf/z131-148.pdf
A thermocouple is classified as a simple device. It will not create or store enough energy to ignite any mixture of volatile gases. If the energy level of a typical thermocouple circuit were plotted on the ignition curve in Figure 4, it would not be close to the ignition levels of the most volatile gases in Group A.
Is the thermocouple which is installed in a hazardous area (Figure 5) intrinsically safe?
The answer is no, because a fault could occur on the recorder which could cause excess energy to reach the hazardous area…