Currently each invitation is sent via email and contains embedded accept/decline options. Growth will include txt/sms as an option, and later, as an app, likely push notification (not yet)... Server-side keeps tally of responses, and on the preset 'need-to-know-by' date, either confirms or cancels event, and notifies accordingly. Hope that helps... thanks for checking in... Michael (to clarify, friends are not sent directly to Zejoop site because it's not necessary that they opt-in just yet... they opt-in if they want to plan an event of their own)