Yes it is posible but I'm not sure I want to take that on right now,
expecial since one already exists for Yahoo's widget engine. Try
contacting Charles Cox, writing of the "oilPrice" widget and ask him
if he will consider porting to Dashboard. If you want to know, I
looked at the code and it looks like he scrapes
http://www.wtrg.com/index.html for the current price. When 10.5 comes
out, you should be able to use one of the new widgets to create your
own gold widget.
If you have no luck contacting the author of oilPrice, write back and
maybe I can be persuaded.