The best UI I can think of is if you press and hold on the link field, the UI popup should appear (as it does in Safari when you press and hold a link) and the options "Open in Safari" and "Cancel" should be available (maybe even "Open" if you want). (In addition, "Copy" should also be there if you end up implementing the other feature I requested).
I know that you can press the link to open it up in the built in browser and then from there open it up in Safari. It's would just be quicker and easier if this feature was available though. Plus if the page takes a long time to load, you would have to wait for it to load twice using the current method.