[ecfisa]

Hola pape19.

Si no te entendí mal, podrías hacer algo como esto:

Ventana con cuenta regresiva:

Código Delphi [-]
...
type
  TForm2 = class(TForm)
    Timer1: TTimer;
    Label1: TLabel;
    procedure FormCreate(Sender: TObject);
    procedure Timer1Timer(Sender: TObject);
    procedure FormDestroy(Sender: TObject);
  private
    FCountDown: TTime;
  public
    property CountDown: TTime read FCountDown write FCountDown;
  end;

var
  Form2: TForm2;

implementation {$R *.dfm}

uses DateUtils;

procedure TForm2.FormCreate(Sender: TObject);
begin
  BorderStyle:= bsNone;
  WindowState:= wsMaximized;
  Color:= clBlack;
  Timer1.Enabled:= True;
  with Label1 do
  begin
    Color:= clBlack;
    Font.Name:= 'Verdana';
    Font.Size:= 72;
    Font.Color:= clLime;
    Left:= (Screen.Width - Width) div 2;
    Top:= (Screen.Height - Height) div 2;
  end;
end;

procedure TForm2.Timer1Timer(Sender: TObject);
begin
  FCountDown:= IncSecond(FCountDown, -1);
  if FCountDown > 0 then
    Label1.Caption:= FormatDateTime('hh:mm:ss', FCountDown)
  else
  begin
    MessageBeep(MB_ICONEXCLAMATION);
    Close;
  end;
end;

procedure TForm2.FormDestroy(Sender: TObject);
begin
  Timer1.Enabled:= False;
end;

end.

Llamada:

Código Delphi [-]
...
implementation

uses Unit2;

procedure TForm1.btnDescansarClick(Sender: TObject);
begin
  with TForm2.Create(nil) do
  try
    CountDown:= StrToTime('00:01:00'); // 1 minuto de descanso como ejemplo
    ShowModal;
  finally
    Free;
  end;
end;

Saludos.