Is there any way to replace the back button using an application? I own a new LG Optimus One. The buttons on the set are somewhat stiff. When I press it it feels as if it might break/get stuck somewhere in the near future. I was mainly concerned about the back button as it is used very frequently and has the maximum chance of having problems.

So I have been looking for an application that can help me use the back button. So instead of pressing the existing back button I would use the touchscreen to get it done. Any ideas?
This is possible if you're rooted. There's two applications that I know of which give you a little persistent overlay on the side of the screen, then pop out a full set of soft buttons when you press the overlay. One is SoftKeys, the other is Button Savior.

I haven't seen anything equivalent for non-rooted devices, but there is an app called SoftHome which adds a home button to your notification bar. It doesn't have a back button, however, just home.