I'm getting pretty annoyed with these voip apps.... I've tried Skype, Dell Voice (Fongo), Viber, Kakao Talk, and many others. I find they're not reliable, because after reboots and whatnot, you get "signed out". You may not know it and its difficult to remember and type passwords/usernames to sign in. So I don't see how they can ever try to compete with your mobile phone service - which doesn't require that you "prepare" your phone every time someone calls. I'm trying out voip apps, because I would like to call and receive calls from someone in another country (mexico) on my mobile - for free. I'm looking for such an app that won't sign itself out, or better still, does not require that you sign in! Does such an app exist?