Continuously variable gearboxes do they exist as separate parts?

[KingNothing]

I'm sure many of you are aware of CVTs or continuously variable transmissions. Many of you are also aware, I am sure, of off-the-shelf gearboxes which you can use to step up/down (typically) the output of a motor.

Do they have a device which allows a variable gear ratio, especially one controlled by an electrical signal?

 

[Unrest]

How about this

http://www.piv-drive.com/gb/9000.asp