How do I update the serial monitor without printing a new line each time? I'm testing out an accelerometer and I want to know if there's a way to make it so that the serial monitor will update the values without printing a new line. Ideally the serial monitor would say something like:

Accelerometer X: $xval
Accelerometer y: $yval


and then instead of printing two new lines each time, it just updates the values. Is there anyway to do that in Arduino? Thanks.
The ultra-basic "serial monitor" in the Arduino IDE cannot do what you want.

Instead you need to either write a special client program, or use a more standard serial terminal program, such as Tera Term (Windows), Minicom (Linux), etc.

These standard serial terminal programs use a special sequence of characters called ANSI escape codes which manipulate the display, doing such things as setting colours, moving the cursor around, etc.

More information on ANSI escape codes can be found here: http://en.wikipedia.org/wiki/ANSI_escape_code