So I ended up going a path that I have not seen traveled previously. I have a S2000 that I'm tracking but I also autocross and drive on the street. I'm installing an oil cooler on it and am somewhat concerned of temps getting too low on street highway driving and possibly for autocross events. Obviously good to monitor temps on track but I'm pretty sure my 19 row Setrab cooler will be sufficient to keep things in check for 25 minute sessions on a car that I've already run in stock form. The purpose of my temp gauge is moreso to monitor the extremes than be sitting there looking at it. I'd like to hopefully cure thermal runaway or at least minimize to to keep things below like 240 degrees or so for longevity. I didn't particularly want a gauge or to setup wiring, blah, blah... The sandwich plate I'm using on the oil cooler has a 200 F thermostat where just about every other one I found on the market was 180F. I couldn't find a 200 F sandwich plate with a sensor provision hence I went with the drain bolt plug. I'd prefer to monitor at the sandwich plate but hoping the pan will work out fine.
I did some searching and found a wireless temp gauge that connects to an app on your phone. The same company offers a pressure sensor as well, if needed. They claim auto is a good application for their sensors and picture a C6R. Sensor was $185 and I had to email them to get an invoice and have on sent out. They were pretty responsive. I have yet to truly use it but their app is good enough and looks like it'll log some temps. Check the Phoenix Sensors link for their site. Below that is the link for the drain bolt tapped for a sensor.
wireless temperature sensor, bluetooth wireless sensors, wireless temperature sensors, OEM wireless temperature sensors, Temperature transducers
phoenixsensors.com
The STM M14x1.5 engine oil pan drain plug is machined with an 1/8" NPT temperature sensor provision to allow you to install a temp sensor right into your drain plug. The plug itself has a M14x1.5 thread which fits most Mitsubishi including DSM, Evo and 3S and some Honda, Acura and Mazda models.
stmtuned.com