Originally Posted by Turtle91
If you haven't seen the "Marvin" reader yet, you should really take a look. It has really taken ePub 2 to new areas (like what you are talking about here). It is currently for iPad only but the developer has already started on iPhone and plans android after that.
It is hands down better than any other reader I've seen...and free!!
My understanding is the ePub 2 spec does not allow external links. I will look at Marvin, thanks for the suggestion - but if it is iOnly, or iSpecific, I won't be using it.