There are a lot of similar services to SlideShark to control presentations from an iPad. For the most part our application is really designed and best served from a full desktop computer right now.
My recommendation for iPad users would be to use our Office 365 application to present our polls from the PowerPoint App for iPads. You can install that here and then work within PowerPoint with your iPad.
Install:
https://store.office.com/poll-everywhere-WA104218073.aspx?assetid=WA104218073