2 android apps, one to send dtmf from sip header and the other to dial and respond to dtmf

I have posted this project before and many bid without knowing what they are bidding for. If you are interested: PLEASE WRITE A FEW LINES OF YOUR UNDERSTANDING OF WHAT THE APPS DOES. Bids with no summary will be deleted. We will have 2 android phones They will be connected by a (crossover) 3.5 mm cable. On phone 2 you will create an app that will listen to headset mic for a dial command followed by the numbers to be dialed. This app will listen for a voice dial or dtmf dial from the headset jack and dial out the number it hears. Examples of response When a dial is received, issue a tone to acknowledge (*1). when ringing begins, issue a tone (*2) . if busy/congestion/not available (*3), when call has been answered *4, when call gets hung up (##), (let me know of other possible codes that exist) On phone 1 You will create a app which accepts SIP calls and generates dtmf or voice dial commands based on what comes in the sip header. the sip app will register to a sip sever who will send it numbers to be dialed in the header When the sip server sends a call, the sip app will issue dial command via the headphone speaker. (to phone 2) if it hears a acknowledgement that the dial was received, wait if no acknowledgement in x seconds (a variable default 20), issue a sip cause code 503 to sip client If busy/congestion/unavailable etc issue 503 if ringing received issue sip 183 If busy/congestion/unavailable etc after ringing issue 503 If answer signaled is received , issue a success signal on sip side, I believe it is sip 200 If a hangup signal is received, issue a hangup on sip side, i believe sip 487 Sip client on phone 1 will only register to sip server when it detects that headset jack is being used. If you can also make asterisk work as phone 1 (using chan_alsa) Please mention.