Sensors > 5v analog > RS232 conversion > 2.5mm Stereo Jack > Tactrix > Happiness You'll connect your sensors to an a device than can receive their 5v analog input and transform it an RS232 data stream which will be sent to through a 2.5mm Stereo Jack connected to the OpenPort jack input and add a bit of configuration and that's it.
Technically something like this could work but I haven't properly read the documentation nor do I own the product. I use an Arduino+MAX3232 but you could technically use anything that is able to produce an RS232 signal/stream that respect the OpenPort protocol. This won't be a very detailed how to but you should be able to get the idea. Long story short, I've found out that Tactrix has RS232 input which can be used very easily to add any amount of external sensor, eg: oil pressure, fuel pressure, O2 sensor, Knock sensor, WMI flow sensor, etc.
