I'm trying to create a native block for a hardware sensor. I've got it working pretty well, but can't get it to show up in the "port view" as anything but a sound sensor. I really need the live view of the data the sensor is seeing. Is there an example of how this is done that I could follow?
The answer is: you can't.
The EV3 brick detects which type of sensor is plugged in to the ports by examining the electrical characteristics of the sensor1. Electrically, all NXT Analog sensors look pretty much the same, so they will all be detected at the LEGO NXT Sound sensor (or possibly the LEGO NXT Light sensor - or a very, very small chance as the LEGO NXT Touch sensor).
So, take @momrobo's advice and write a small program that simulates the built-in port view.
Or, if you are really ambitious you can create an adapter so that the sensor will look like an EV3 type analog sensor instead of an NXT type analog sensor. How do to this would be better suited to a blog post.