string contents;
using (var wc = new System.Net.WebClient())
    contents = wc.DownloadString("http://herbiteam.me/workspace/YuriWork/isready.txt");

if(contents == "1"){
//WYŚWIETL OBRAZEK / MENU Z INFO O DOSTEPNYM GOOGLE PLAY
}else{
//PRZEJDŹ DO GRY CZY CUŚ
}