Photographing a proposal

I was catching up on my wedding reading just now and came across this very interesting story in The New York Times about marriage proposal photography, Will You Marry Me? Say Cheese!. I know the photos I took immediately after proposing to my wife are some of our favorites and it would have been great to have had some of her reaction when I proposed (as much of a photographer geek as I am, I didn't have a camera in her face when I asked the question). I know couples who've gotten engaged at Castle Hill or on the Cliff Walk and I think it would be great to be a "bystander" who was there to photograph the very special event. In reality, I have a great zoom lens so no one has to be in anyone's face. Anyone interested?