[NumLock]

GetKeyboardLayout function
Language Identifiers
Language Identifier Constants and Strings

Код:

var
  hForegroundWindow: THandle;
  idProcess: DWORD;
  hKeyboardLayout: HKL;
  sTip: String;
  sIcon: String;
begin
  hForegroundWindow:=GetForegroundWindow;
  idProcess:=GetWindowThreadProcessId(hForegroundWindow);
  hKeyboardLayout:=LOWORD(GetKeyboardLayout(idProcess));
  case hKeyboardLayout of
    $0409: begin
      sTip:='Английский';
      sIcon:='ENICON';
    end;
    $0419: begin
      sTip:='Русский';
      sIcon:='RUICON';
    end;
    else begin
      sTip:='KeyboardLayout';
      sIcon:='UNKICON';
    end;
  end;
end;