Got inspired by an app on a blackberry. Wish to have something like that on my N900:

Having a quickly accessible key combo or finger gesture for setting the phone in a mode, that doesn't show anything on the desktop except the background picture. In this mode the phone should not allow anything except dialing, starting and finishing a phone call. Repeating the key combo or finger gesture should return the phone to standard mode and enable again all widgets.

It would also be nice to have that option during a phone conversation.

Use example #1: I want to borrow my phone to somebody (business partner), so he can make a quick call. No need that he can see my latest incoming messages, my calendar or my at this moment running apps.

Use example #2: Having a phone call and then letting a friend talk to the person on the phone. The person may not be used to touch screen and see personal information or start tasks, that will cause unnecessary complications

Use example #3: Showing the desktop background picture to somebody. Without having all those thumb nails and widgets covering the background.

In a phone like the N900 use case #3 is not typical but use case #1 and #2 made me wish several times already to have that kind of app.

Can it be done? Is anybody on it already?