How to interact through the window

vvvv beta question
1

Hi guys, do you know how these guys could use those stickers as buttons?

2

capacitive sensor

http://www.sensorwiki.org/doku.php/sensors/capacitive

3

looks like they are using paint from bare conductive, along with a touchboard it should be pretty easy: http://www.bareconductive.com/shop/touch-board/

4

Thanks tekcor.