AirPhones has been a fun project created with extremely limited resources. We have a volunteer working on the 4.0 compatible update, which should be available in the coming weeks. I wish all along that this project had the resources to make it as big as I've always imagined, unfortunately reality has proven otherwise. Many thanks to our volunteer programmer, I am humbled and very grateful for your efforts.
Anyway, there should be an update coming soon, which will address some of the user issues and make for an even better experience, with background app support as well.
Thanks for everyone and your positive support & feedback.