When developing for mobile (via mosync for example) you can choose to do stuff in C/C++ only, but if you want to read in websites and alter them with C/C++, you'll need a html(5) parser available first of all. Luckily android and ios are capable of doing just that, and mosync has template projects that cover the parsing for you, you just need to catch the events that come in via wormhole in C/C++. But if you need to do a bit more than just receiving and sending you need to know javascript/html5 too in order to extent both frontend and backend.