Smart Technologies has the solution to the "how to access a SMART Board from an iPad" question. They offer an iPad app called SMART Bridgit Conferencing which solves the problem and makes your Board remotely accessible. Multiple users can write on the same display. Features include: wifi connection, intuitive toolbar to access tools, seamless integration with Notebook software, all the benefits of online meeting software so it works in an e-learning environment. I'm wondering if it's time to but a used iPad to test this.
Good news: the app is free so any of your students can download it.
The catch: " Access to a SMART Bridgit Server version 4.2 or later is required to use this app. For more information on SMART Bridgit conferencing software, or to learn more about SMART Bridgit server software," so you'll have to contact your reseller for a price.