Temporarily protect email/sms when giving device to others? Say my cousin wants to play with my phone/tablet for a while. Let's pretend I'm really nice and pleased to let him play with it as long as he wants, but deep inside I'm a little worry about him reading my emails and sms out of curiosity. And I have other things to do so I can't stay around and watch.

If the current GMail or SMS applications don't have a 'temporary lock' feature, is it possible to write a separate application that controls access to existing applications on the device? For example, something like "com.google.android.gmail.Main is temporarily protected, draw the correct pattern to open".
Give this application a try App Lock you sound be able to lock the application you want to keep private.