Oil temp is in VCDS. I believe it is in the Instruments section, but I will check later. The sensor in the bottom of the oil pan reads both temp and level, but the temp reading is not “attached” to anything on the S4 for some reason (my Touareg has an oil temp gauge, go figure).
And confirming Bs comment on the oil pressure switch. It only reads on/off. Once the pressure drops below a certain level it triggers the warning, but it does not send a reading that varies based on the oil pressure. I also agree with the the suggestion on running a line from the distribution block where the stock safety switch is. The 1.8ts are set up this way for an oil feed to the turbo. My guess is with the consistency of Audi in the way they engineer things, the distribution block is probably pretty similar.
Edit: Added VCDS readout…
Below are readouts from Instrument (17) section of VCDS on my B6. Measuring block 50 is oil temp…
http://audirevolution.net/addons/albums/images/237891629.jpg