I don't know of any apps specifically except for Torque, but that can be a little laggy. I don't consider it real-time.
I've looked at these units and similar from Amazon, Flea-bay, etc.
They require OBDII to interface.
There is also the Trail Tech units. While designed for MCs, they could be easily adapted to a truck
Are you looking for an easy way to get gauges or are you really gunning for a glass-cockpit arrangement?