We have built static libraries that work for both iOS, and also for Android: using the Android platform notes presented here
Minor edits to the code should make poco work using stlport_static. but using gnustl_static works out of the box.
the iOS static library work out of the box in Xcode using: c-dialect:GNU99, c++-dialect GNU++11, C++-library libc++ and the LLVM 4.2 compiler.
GCC_C_LANGUAGE_STANDARD = gnu99
CLANG_CXX_LANGUAGE_STANDARD = gnu++0x
CLANG_CXX_LIBRARY = libc++
(One tiny edit might be needed on version 1.51 of poco for iOS and Android, if stl-library version you have is different from the std:: namespace used in Poco).