It definitely could work from what I see on Amazon. I didn't even know a product like this existed for after market installation. Seems to be a good deal on Amazon too. I think that the keyless entry is especially nice to have on a work vehicle.
I do know it is a hit among Sprinter users, and I read that the install hinges on how well the glass is cleaned before applying it. However, from there... no clue. The ProMaster likely has a different computer than the Ducato, so it would be interesting to find out more info on this, if it is compatible.
For me, it would be nice when boondocking. Before a hike, I can toss everything in the motorhome, put the keys in the strongbox, and head out. That way, I don't have to worry about losing keys. Of course, it is good to have a backup place on the vehicle if the batteries die, but being able to punch a code and get in will help immensely.