Help Rejecting a call without the caller knowing?

[basalt]

I wonder if there's a way of doing this - it would be handy to be able to reject a call so I can carry on listening to music etc but leave it ringing from the callers end so they don't know I've done it.

 

[lilien98]

I think I heard about an App doing this. Just search the market for call blocker or something similar...