That'd be useful if there was one that didn't have a goose neck (my cig. lighter is where the the corner at the base of the dashboard center console, and the between-the-seats center console; it's a 2000 Saturn LS200). Maybe a multi-segment column that could be oriented like a gooseneck. Or an articlated conduit type holder (like many dashboard holders have -- or is that what you meant by gooseneck? I think of goosenecks being like the trailer hitches or cleaner bottles that are rigid but somewhat S shaped).
And, in order to keep it from draining the car battery, it'd be nice to have a switch on it that would make it draw _no_ current at some points in time. Most cig. lighter power plugs I've seen still draw power even if you have nothing plugged into them.
Last, have it be useable in both portrait and landscape (have it be rotateable, and have it hold the phone in a way that you can open the screen when it's in landscape orientation).
But, yes, having something like that for the G1 would be outstanding.