What I do when I turn the silent switch on is that I also open an app that I rarely use and while the app is open I press the Sleep/Wake button at the top of the screen. This locks the screen and the next time I unlock the screen, the rarely used app is there instead of the normal home screen and that reminds me that the switch is on. If that isn't enough, you could use the same approach but leave the Notes app open with a note re the switch. Either works for me for a short-term use of the silent switch (e.g., while at a movie) but isn't a great solution for a longer term need when you might need to use other apps while in silent mode.