I promised to keep the Community updated regarding the link to Prode Properties when Prime 3 was available. The dll needed for the link is available on the PTC website and on my website . The dll had to be rebuilt because Prime is a 64 bit program whereas Mathcad 15 is a 32 bit program. My website tells how you can use both the MC 15 and Prime 3 versions with Prode.
There were some problems with the Prode functions that return string variables, but John Sheehan got that fixed. Everything is working okay now. I changed a few things in the test file to make things a little easier, but that had nothing to do with Prime.
Yes, you can work with units. The test file gives some examples, but it doesn't show units throughout. Basically, you multiply a Prode result by the default Prode units for that variable. Then you can use the variable in the normal Mathcad way, displaying the value in other units as needed.
My first answer only dealt with the output variables. The input variables do need to be dimensionless, using the implicit dimensions currently set by default or by the user for that property. Thus, an input variable with explicit dimensions (e.g. pressure in Pa), can be divided by the unit in the argument list. That is the rest of the story.