Overlays are great for different tactile feedback, but at the same time they need to be done right. We think that the magnets on the Sensel are to weak to really hold the overlays firmly in place while performing gestures on them. Since we are working with capacitive touch on the Tickle, all materials with air enclosures will reflect the capacitive field so they make finger detection less robust to impossible.
The next generation will be running on resistive touch technology, so we can re-think overlays with it.