O I was reading this article of some old phones by fujitsu, and I found that this feature was interesting and could be useful for specific groups of people - from corporate, security, and even government...of course not forgetting those who juggle multiple other R/s lol.
Japan's Philanderers Stay Faithful to Their 'Infidelity Phones' - WSJ.com
1. keybuttons to enable and disable privacy mode
2. No one knows that privacy has been turned on or off - maybe some subtle difference.
3. All information that is tagged private (SMS, emails, Phone numbers, phone calls, miss calles, phonebook entries) are hidden under privacy mode.
4. In privacy mode - the phone does not ring - but maybe route to some hidden mailbox, arriving sms/ emails does not show by ringing phone)
5. Documents / objects in the phone tagged as private does not show in this mode - good for security, government etc.
Possible to embedd this features into OpenOS?...it will surely get some interest in specific groups of people