I've contacted P3 and they are going to be bringing out a revised version of their M135i display that will include oil temp amongst the metrics!
I'm definitely going to get one.
And as mentioned above, the boost reading can be made compatible with a piggyback ECU tuned car, i.e. it can read the actual boost pressure, which is cool.
I like the integrated look and the fact it still allows the vent to work, unlike a lot of vent-mounted gauges.
But for any proper track driving, oil temp is a must.
Incredible BMW don't allow it to be displayed on the multitude of displays already on the car. I wonder if the M235i will be the same?