You could log out of the iCam app so it doesn't automatically access your cameras if someone else did open it...that would be the easiest way to prevent viewing. In addition, I believe you can have blank "desktop" screens on your iPhone...so as you swipe right-to-left to browse through your apps, I think you could have a blank "desktop" area or 2, then finally have a last "desktop" area with iCam on it. Or you could bury the iCam app in a folder and make it hard to find.
You could also just delete the app and reinstall it (doesn't take long).
If you are committed to actually hiding it, I think your only other option is to jailbreak your iPhone (free). There is a feature that allows you to hide apps (free). In addition, I know there are Cydia apps (not free) that can lock apps and require a password to access. There might be a similar app in the iTunes store (not free), but I'm thinking not.
