you can indeed do this, using gstreamer to route the audio streams over the network. {since you have mouse control, you dont really need the dbus commands to make calls, but it would be less strain on the network to simply ssh in and use dbus commands}. this doesnt require google voice or anything else at all; vnc access would be completely sufficient.

an easier solution to your problem, though, is just to setup call forwarding when you forget your phone. you can set up a google voice account now, and have it ring your cell phone when someone calls it. then when you forget, simply turn off the forwarding and have it ring your computer.

OR you could set up a google voice account when you forget your phone, and then contact your phone service provider and ask them to set up unconditional call forwarding.