My full paper, “Tactile Feedback for Above-Device Gesture Interfaces: Adding Touch to Touchless Interactions”, was accepted to ICMI 2014. It was also accepted for oral presentation rather than poster presentation, so I’m looking forward to that!
In this paper we looked at tactile feedback for above-device interaction with a mobile phone. We compared direct tactile feedback to distal tactile feedback from wearables (rings, smart-watches) and ultrasound haptic feedback. We also looked at different feedback designs and investigated the impact of tactile feedback on performance, workload and preference.
We found that tactile feedback had no impact on input performance but did improve workload significantly (making it easier to interact). Users also significantly preferred tactile feedback to no tactile feedback. More details are in the paper  along with design recommendations for above- and around-device interface designers. I’ve written a bit more about this project here.
The following video (including awful typo on the last scene!) shows the two gestures we used in these studies.
 Tactile Feedback for Above-Device Gesture Interfaces: Adding Touch to Touchless Interactions
E. Freeman, S. Brewster, and V. Lantz.
In Proceedings of the International Conference on Multimodal Interaction – ICMI ’14, pp. 419-426. 2014.