I'll try to explain everything point by point:
"No marked deck"
This is correct. No marked decks are necessary.
"freely chosen"
Yes, the card is freely chosen. No forces.
"borrowed mixed deck"
The video below uses a borrowed shuffled deck and it shows you everything you do to make that work.
"No peeks"
You never see or peek at the selected card. After they pick it, they hold onto it the whole time. You do look at other cards in the deck but that's not generally what we think of when we describe a peek.
"The cards do the heavy lifting"
The cards and the app work together to do the heavy lifting. This trick isn't relying on the cards to do everything for you.
"Do you tell the app the card?"
You can. After you determine the card, using the app, you can then reveal the card. Or, you can tell the app the card and reveal it through the app.
Oh, and here's an uncut video performance:
https://www.youtube.com/watch?v=eRwTvI2W7kw
