Your could set the default values of the controls to values that would never occur if real data is sent in; then when the VI runs compare the value in the control to the default value.
To actually determine if a pin is wired, you need a reference not to the VI, but to the instance of the subVI on the caller's block diagram (which would only be accessible in the development environment). However I don't know of any way for a VI to determine from which subVI instance it was called.
It might be possible to do what you want with malleable VIs.
Or as a last resort, XNodes.
"If you weren't supposed to push it, it wouldn't be a button."
