I'm a programmer working with an intellectual property attorney to develop an attorney-based website. According to what he has told me,
Two or more actions on the web count as a legally binding action.
This could be a click and a confirmation, a signature and a "submit" action, you get the idea.
DISCLAIMER: This information is only valid for the United States (as far as I know), and for educational purposes only, do not trust it, etc...
My advice: build your application and then worry about the legal issues later. Those problems are good problems.