Available in both free* and full version (from version 1.6.1 - Sep 2015).
Here is an example on how iPad multitasking looks on iPad Air 2 or iPad mini 4+:
Which iPads will support iPad multitasking? Right now those will be iPad Air with iPad mini 2 and 3 to support a "Slide over" and iPad Air 2 with iPad mini 4 supporting fully blown split view screen.
So excited you'll be able to use speedometer with any other app sharing iPad's screen! That's about productivity and Apple has really raised a bar on that!
* Free version 1.6.1 is limited a bit with iPad multitasking. Please setup all the speed limit presets and everything else in the app before using multitasking as popup "edit speed limit" and feedback windows don't work well in free version 1.6.1 when multitasking in "slide over" mode. Everything else works fine. This is not an intent from us, just time pressure constraints when pushing iOS 9 versions to Apple. Next free version will fix that. Full version 1.6.1 has no limitations in using iPad multitasking, both slide over and split view.