<MyLabel@Label>:
    text: 'Current Temperature: n/a'
#    on_lastTemperature: self.update_current_temperature_label()

<MainWindow>:
    label_wid: "Temperature Monitor"
    BoxLayout:
        orientation: 'vertical'
        BoxLayout:
            size_hint_y: 0.1
            orientation: 'horizontal'
            MyLabel:
                id: 'current_temperature'
            Button:
                text: 'Start/Stop'
            Label:
                text: 'No File Chosen'
            Label:
                text: 'Data Source'
        Label:
            text: 'Graph placeholder'