This should be achievable using a shortcut rather than a widget.
Long press home screen, select Shortcuts, Direct dial, then the contact number you want.
That's using a rooted N1 running 2.2, if those options are not available, then download Any Cut from Market and then do this:
Long press Home Screen, select Shortcuts, Any Cut, Direct call, then the contact number you want. You can then edit the shortcut name before it gets added to the screen.
Both implementations add a shortcut, that when selected, opens the dialer and places the call.