While the function is still not available on the SlingPlayer for iPad. You are able to stream in the background with the latest version of the SlingPlayer for iPhone (Version 3.7.34). The reason I mention this, is because, if you have the SlingPlayer for iPhone, you can download the SlingPlayer for iPhone on your iPad and will be able to use the multitasking function with your iPad. Please see the following article.
If you have any issues or questions, please let us know.
Hope this helps,
Sling Media Moderation Team