asterisk users - Apr 2009 - one-button call parking/pickup on Asterisk with Polycom phones?

Anyone want to talk briefly about one-button call parking/pickup on
Asterisk with Polycom phones? Does anyone use it or know to do it?

On many phone systems there are 2 or 3 park buttons, and you can park
a call onto an unlit park button, and then the light flashes.  You can
go to any other phone, and press the park button with the flashing
light to pick up the call.

Super easy from the user's point of view.

How to do with Asterisk? Hints?