Like Kelmar said, a auto-lock time out setting coupled with a pin lock entry code secures your phone from prying eyes.
If your worried about someone rummaging through your phone after you've loaned it to make a call, then man don't lend out your phone.
If the desire to be of help over rides your paranoia, simply pull up the task manager, press the remove all, and poof all evidence of what you were doing is gone.
You seem to be making a issue out of something that's not really an issue. If there was no way around any of the things that your bringing up, then I would be on your side all the way. This isn't Apple, you don't have to wait for them to supply you with the way to do things.
The sound issue can be solved with the app Audiomanager. You can set up various profiles that can be accessed easily.
Hope that you don't take this as a attack, because it's not. Just commenting on your perception of things.