You cannot however use anyone else's GPL code while doing this, because those library authors didn't give you permission to relicense their code. It closes off

You cannot however use anyone else's GPL code while doing this, because those library authors didn't give you permission to relicense their code. It closes off the entire Play Store to the GPL. This is the same thing that caused the FSF to declare Apple's iTunes store as incompatible with the GPL. Curiously, I think the iTunes TOS clause that disallowed copyleft has since been removed, but I haven't heard anyone more qualified than I offer an opinion on whether you can now publish GPL iOS apps.