If you're talking about frequency hopping, I suggest you take a look at this thread over at thisisant.com (requires registration, but is free). I think it should cover what you need.
That's a very different question indeed. For this you have to use the S120 SoftDevice, and there are Central examples available in SDK 5.2.0.
Anyway, since my original reply answers the starting question, I'd be happy if you could accept it, to clear up this question. If you have further questions on the Central capabilities, I'd recommend you to search first, and then post separate questions if needed.
