In Arduino 0019 I see they have introduced a command called Serial.peek().
However, what it does appears to be a complete mystery as there is no mention of it in the reference pages and not even any documentation for it on its own google code page.
If anyone can shed any light on this mysterious new command please let us know as the developers obviously don't want us to. Thanks.
Look at the source code.
I would guess that it reads a character from the serial port, but let it stay in the input buffer so it can be read again.
If it's like most other "peeks" it reads one character from the buffer but does not remove the character. Typically, peek is used for "look ahead" when parsing data.
This seems to be a good description...
Here are some notes that I have found.
http://code.google.com/p/arduino/issues/detail?id=60
I was trying to find some good examples of how it is used. I will look at the wiki article to see if that will give me a better understanding.