Oop, spoke too soon. With the current release of 1.5.7.2, Im still finding that there is no way to restrict a widget's display between tablets and smartphones.
In the device setting (for my slideshow widget), I can only check these boxes.
[ ] Desktop
[ ] Mobile
Just like Wordpress' wp_is_mobile function, it defines mobile device as any sort of touch device. So, Im still unable to specifically target smartphones as the one to hide this widget but allow tablets to still use it.
Is the next rendition of your beta able to differentiate tablets from smartphones? Is this even possible?