Worked as described!
I connected Surface 3 pro with my iPad Air 2, and it worked with no issues! I tried a few other second display app (splashtop, Airdisplay.) This app is the only app working properly.
Just keep in mind that its PC app, which is required to use this app, takes a slight CPU load, between 10% and 20%. This means that is drains your laptops battery, making this app not recommend without a laptop charger.
ABUMtech about
TwomonUSB - Extended Display