Yes, there is the physical switch that turns red when the ringer is silent.
But ALL of the iPhone's usefulness is on the screen. All the other physical buttons (Home, up/down volume, lock screen/power) can all be accessed by feel and do not need to be physically looked at to be useful. But of the ringer switch, in which you need to look at it (how do you do that in the dark?!) to determine if your ringer is on silent or not.
You could of course simply switch the switch and there is a splash of Ringer or Ringer Silent on the screen for a moment, to determine silent mode. But constantly flipping this switch many times a day to determine the status of silent mode is prone to wear out this switch and render it inoperable. Unless of course you get a new iPhone every year.
Every single cell phone I have owned (until now, with the iPhone) since 1998 has had a silent icon on the screen when the ringer is turned to silent. Actually, when vibrate became a feature of cell phones over 10 years ago, usually the icon showed either a ringer-off (total silent), vibrate (vibrate on ring) or no icon (normal ringer).
I realize Apple likes to be different, but this is just a plain headache.
I have sent two different requests to Apple to implement this feature, hopefully they will fix this soon!