I understand that the normal development environment for Androids is Java, or some look-alike. But there seems to be a gcc around for it, too; how hard would it be to to port my homebrew C code, written for the Liunux environment, to Android? More generally, how feasible is apps dev on Android in C?
Android is basically Linux under the hood, and you are absolutely correct that C or C++ code can be compiled with Android's version of GCC using the NDK (Native Development Kit). Many organizations do this as a way of having their core functionality portable across different platforms, while using Android's Java APIs for the user interface and other "glue logic".
In fact, it recently became possible to write entire Android apps, including user interaction, using C/C++ rather than Java.
(I am also a software developer for Android and other mobile platforms.)