For those under 18...
We are still requiring a hard copy form to be turned in. They receive a link for this form in the confirmation email that we get.
We also use a yearly waiver that parents can sign once a year giving permission for any event. If they have a yearly waiver on file, than we don't need anything else.
For those over 18...we just write up the release in the question instruction section. The question is then, "do you agree with the conditions of the medical release and liability form?" and they answer using a drop down box of yes/no.