Since there is no direct way to detect the changes of memory in SD Card, SDCard Droid updates itself:
1. every 4 hours
2. every time screen is on
3. every time SD card is mounted/unmounted
4. every time app is installed/cleared
5. every time camera button is pressed (not sure)
To install widget, long click on any empty space of home screen. A dialog will prompt. Select Widgets and choose SDCard Droid in Choose widget page. Then, a widget will appear on home screen.
The other way to install widget is to press menu button on the phone and click Add. A dialog of Add to Home screen will also prompt.