The most popular PTT app on android just became available in App Store. Its called TiKL. Unlike the existing so-called PTT apps that do record-then-send, TiKL instantaneously connects you with your family/friends for a private conversation. It supports group talk as well as one-on-one. I am impressed how well it works between my iphone3gs (iOS4), ipod touch (4th gen) and my wife's android. And it is completely FREE! All you need is a facebook account. Tell all your fb friends about it. 