I'm a little out of my depth here as I don't have Sky and I've never heard of the device you refer to.
However looking at one on Amazon seems to suggest that it's only useful for Sky 'on demand' services, for which you need a subscription.
From your previous posts I'm assuming that you'll have no subscription associated with the 'spare' Sky+ box, so I can't see that how an SC201 device would be of any use to you.