there's now an iphone app called linksinablink that seems to do this pretty well, if you are signed up to foxmarks (or xmarks as it seems to be called now). it doesn't put your foxmarks into safari on the iphone but no problem - when you click on one of yr bookmarks in this app, it fires up safari.
If there's a downside, it's that it doesn't sync any bookmarks you set up on yr phone - it only downloads them.