"How do you hang up incoming calls (in Android of course)?"

First, I know this question has been asked and answered several times, and the response is always "you can't". But if we look in the market we get a few applications (all private software, no access to the source code... :-( ) that do this action, such as CallFilter, Panda firewall and others...

So... does somebody know how these apps do the hang up action, (or terminate, or disconnect or whatever you call it..)?

And other question, if the first don't get a response.. does somebody know how send an incoming call to the voice mail?

Of course, all questions are about how to do it programmatically. So with the voicemail question I know there's a flag in contacts that is used for that, but like I said, I'd like to know the programmatical way.

Thanks all!