VadaXchange iPhone OS client software makes the iPhone into an extension of your phone system.
When you are away from your desk, your iPhone becomes your PBX extension. You can make calls from your iPhone via your corporate PABX and have the call billed to your landline provider.
You can see live calls on your extension on the phone system. You will see call even if they have not followed you to your mobile phone. In fact, this software also works on an iPod touch, which you can use as a hand-held operator console.
You can put calls on hold. When the call is held, it is held on the phone system, not on the phone. On the iPhone it looks like the call was disconnected. When you retrieve a held call, you can retrieve it either on your mobile or on your desk phone - whichever is convenient.