I’ve been a bit of an Asterisk enthusiast for a while now. There are a number of great things that can be done with it and many free services to do this with. One thing that I haven’t seen yet is using the Parked Calls feature of Asterisk to make it possible to move a call from your home phone (which is connected to an Asterisk PBX) to your cell phone.
IPKall offers a free phone number in Washington state which is forwarded to any SIP address. If one were to setup an extension on their Asterisk PBX for the IPKall number to ring to which then authenticates the caller. After authentication, the user can then pick up a parked call. So, the scenario.
You are talking to someone at home. You need to run to the store for some hot chocolate (it is cold now after all 
), but want to continue your conversation. Simply park the call on your Asterisk PBX. Get your cell phone and call your IPKall number. Enter your authentication and pick up the parked call. Presto! You are now on the go without having to disconnect. If you really don’t want to waste much time between, you can even begin calling from your cell phone before you park the call and wait to the last second to park the call.
This isn’t something I could see as just useful for home users but also perhaps for a business where employees are often on the run.