System and method for on-demand presence

1. A computer implemented method for determining availability of a user based on mobile device status, comprising:

receiving, at a first device, an instruction to check a status of a second device;

transmitting a status request from the first device to the second device;

receiving, responsive to the status request, a message from the second device indicating a telephony status of the second device;

disabling, by the first device, an ability of the first device to place a call to the second device when the received telephony status indicates the second device has a call in progress;

receiving an indication that the second device no longer has a call in progress; and

enabling the ability to place a call to the second device from the first device.

2. The method of claim 1 , further comprising displaying the received telephony status of the second device on a display of the first device.

3. The method of claim 1 , wherein if the message indicates that the second device is on a call, receiving thereafter an indication that the second device no longer has a call in progress.

4. The method of claim 3 , wherein the indication is one of a Session Initiation Protocol message, a Hyper Text Transfer Protocol message, or an Extensible Messaging and Presence Protocol message.

5. The method of claim 1 , wherein the telephony status is one of free, on a call, or unknown.

6. The method of claim 1 , wherein the status request is a SIP INVITE message that includes a special header.

7. The method of claim 1 , wherein the status of a second device is automatically checked responsive to a selection of a contact associated with the second device.

8. A computer implemented method for providing a mobile device status, comprising:

receiving a status request from a first device;

retrieving a telephony status for the mobile device;

transmitting the telephony status to the first device;

recording the status request when the telephony status indicates the mobile device is on a call, the status that the mobile device is on a call transmitted to the first device causing the first device to disable an ability of the first device to call the mobile device;

receiving a notification that the mobile device is no longer on the call; and

sending a notification to the first device indicating that the mobile device is no longer on the call, the notification that the mobile device is no longer on a call sent to the first device causing the first device to enable the ability of the first device to call the mobile device.

9. A system for determining availability of a user based on mobile device status, comprising:

a) at least one processor;

b) at least one input device; and

c) at least one storage device storing processor-executable instructions which, when executed by the at least one processor, perform a method including:

receiving, at a first device, an instruction to check a status of a second device;

transmitting a status request from the first device to the second device;

receiving, responsive to the status request, a message from the second device indicating a telephony status of the second device, wherein if the message indicates that the second device is on a call, the method further including:

disabling, by the first device, an ability of the first device to place a call to the second device,

receiving thereafter an indication that the second device no longer has a call in progress; and

enabling the ability to place a call to the second device from the first device.

10. The system of claim 9 , wherein the method further includes displaying the received telephony status of the second device on a display of the first device.

11. The system of claim 9 , wherein the telephony status is one of free, on a call, or unknown.

12. The system of claim 9 , wherein the status request is a SIP INVITE message that includes a special header.

13. The system of claim 9 , wherein the method further includes automatically checking the status of a second device responsive to a selection of a contact associated with the second device.

14. A system for providing a mobile device status, comprising:

a) at least one processor;

b) at least one input device; and

c) at least one storage device storing processor-executable instructions which, when executed by the at least one processor, perform a method including:

receiving a status request from a first device and retrieving a telephony status for the mobile device;

transmitting the telephony status to the first device;

recording the status request when the telephony status indicates the mobile device is on a call, the status that the mobile device is on a call transmitted to the first device causing the first device to disable an ability of the first device to call the mobile device;

receiving a notification that the mobile device is no longer on the call; and

sending a notification to the first device indicating that the mobile device is no longer on the call, the notification that the mobile device is no longer on a call sent to the first device causing the first device to enable the ability of the first device to call the mobile device.