First I tought this cannot be done cause those apps(gallery/music etc..) is closed source.

But then I realized it maybe can be done in a dirty way:

1. Remov the original .desktop files and replace it with a cusomized one that instead starts a "pincode app"

2. If succefully validated: spawn the correct app.

Drawback with this is if people has access to the terminal they still can start ithe apps from terminal (or via ssh)..

I am to lazy to check if possible but could be an idea for someone who is willing to tweek...

And in the case of sendsms console app this can be done very easy using qtmobility and python scripting. I think the is already some kind of testcode for it somewhere...