Hello there and thank you for your answers.
@craig to sum up, here is the idea:
Following the setup of Katsuhiko Inoue, I would like to connect 2 Ricoh Theta S, like that:
2 x Ricoh Theta S
1 x RICOH cable switch CA-3 Wire Remote Control
1 x USB 2.0 to Micro USB 2.0 Cable Twin Head / Dual Plug
Then using Monopod / Tripod with a plate.
To do pictures / videos in 360/3D.
@Svendus your example is cool but 1,5 meters between the 2 Ricoh seems a bit too much, especially for a portable, video solution. On the tests provided by Katsuhiko Inoue, it seems to work pretty well by putting them just side by side.