ORIGINAL: pe reivers
The Venom, which uses an NTC resistor, is not the most professional but I still use it on my engine. (some day I will upgrade to professional thermocouples in the plug washer)
The Venom's tiny battery drains quickly, so I took it out, and soldered leads to the connections. I now use a NiMH cell, that lasts about three months between charges
The supplied batteries are junk, I replaced mine with some 1.5V watch battery that was slightly thicker and it has lasted all summer.