I use asterisk in my project and users login with softphones. I want to grant a person to forward an incoming call to another user's sip account by clicking on a button and answer the call immediately so that the user will be able to start talking with caller.
You need read documentation for you softphones/hardphones. Usualy need add sip header Call-Info: answer-after=0.
So you plan can be
For more info check this:
http://www.voip-info.org/wiki/view/Asterisk+manager+Example:+Transfer