You read the title right. When Nintendo was first envisioning the Wii U GamePad, they prototyped one by taping two Wii remotes to a monitor. They used this prototype to develop roughly 30 Wii U game concepts. It looks pretty cheesy, but you can definitely see how the GamePad was developed from the prototype.
"We used this prototype and two Wii consoles to run simulations for Wii U," EAD boss Katsuya Eguchi said. "EAD isn't a hardware department, but a 'handicraft team' knowledgeable about hardware makes stuff like this. One of the staff members expressed a desire for a game that would gather Nintendo's franchises into a single spot and each franchise would have something to do with the others. It was quite a grand concept. But we were like, 'How do we bring them all together?' We didn't take it too seriously."