password/PIN required privacy system

It appears to me that the only truly effective privacy system would consist of a device or software that would only ring you phone if the caller was able to key in a password or pin that he or she had been provided by you.

I have been searching for such a device without success so far.  I have seen some patent applications for such a device and I believe Verizon once offered a very similar "advanced service" option like this.

Has anyone found such a device?  Perhaps we should form a non-profit organization to develop, manufacture and distribute a product like this.

Perhaps a referendum or ballot initiative to require telephone service providers to provide this service as part of their basic service package.

There used to be a device sold, Screen Machine, that did what you described on a land line.
Incoming calls were answered by the device which would play a recording and the caller would have to key a number to continue to let his call then ring your phone. Early models had you press 5 to continue, later versions let the key press be user defined. And best of all, it was very inexpensive.
I have an early model and it worked well.
Sadly, they are not made anymore nor are any easily findable for sale.
More info on it here:
http://www.familysafemedia.com/screen_machine_telemarketer_ca.html

Now that's a good idea. I've been thinking about it. Only legit calls can come through. It can be implemented, manufactured and sold with the right initiative.

I'm not tech-savvy but I wonder if phones could be programmed to do this by writing your own codes. I've heard of people doing pretty cool things with Linux in particular. If a Nook can be hacked to an Android tablet why can't a phone be rewritten? I don't know, I might be posting a stupid question.

I know BBM's firewall can be set to only receive incoming messages from specific numbers but I don't know about calls and I haven't been motivated to tinker with the one I have as it's pretty junky.

In terms of dovelopement, I know there's a USB for computers which denies access of any kind from anyone not sitting right in front of it. I wonder if a chip could be developed for phones. One which allowed greater manipulation of incoming and outbound connections?
I guess it would have to be free from a network in order to work... I don't know if I would trust an app to do that, it could be exploited by its own nature.

But like I said... I bring nothing to the tech geek dinner table but if someone made a chip I might buy it.

Prior discussion last month about challenge-response phone sentry gadgets (Screen Machine, et al) and their limitations in the current nuisance call environment.

https://800notes.com/forum/ta-5d4e343675a5629/call-blocking-devices

I've daydreamed a long time for a phone number alias system, similar to the Sneakemail concept of creating a unique address for use by a single entity. There have been a few meager attempts at such a thing, always hindered by the sheer paucity of phone numbers which have not already been occupied by mobile devices in the past two decades. Tagging a person's phone number with a sort of virtual extension or passcode to be sent to a personal device is an obvious route, but doesn't solve the essential problem of exposing the "real" base ten digit phone number to everyone.

One solution may be having a third party intercept all inbound calls, which would then bounce, block, destroy, delay, or allow each call according to a subscriber's rules. The callers would be given only a phone number of the third party service while the callee's "real number" is kept secret. A unique passcode system could also be part of that scheme. Managing false positives could be a real chore, however, given all of the "privates" and "unknowns" which are innocuous and/or welcome by a person.

Res,

All more-or-less doable.  Start here: <http://www.asteriskdocs.org/> .  Might even be profitable.  Let me know when your IPO hits. ;^)

Or just set yourself up like I did, and enjoy watching the telephone bugs splat against your windscreen.

Nothing like the peace of a phone that never rings unless it is a call you want to answer.

When commenting I did think of your discussions of PIaF and VOIP. I'm not the guy to promote the tricked-out system you run, which has many attractive advantages. Its VOIP dependency for the moment won't serve the broadest possible user base ... at least until the old telcos get their secret wish to cut down all the landlines from the poles.

The ideal desired by the OP is another gadget at a two-digit price you can put to work right from the shrink wrap. It's hard to recommend those things now since they are all built inflexibly in reaction to a particular nuisance call environment which is bound to change. My sentry service idea would in theory be agnostic to the type of carrier service, a 'best of most worlds' deal.

As to a referendum for Baby Bells to advance this cause, that's really dreaming. They are all still living in "entrenched monopoly" mode, where it suits them to either move slowly or not at all. You notice all the innovations in call management have come from upstart manufacturers and companies born in the digital domain, firms with no stake in the survival of decaying business models.

You could set your cellphone to silent, then add an audible ring to everyone in your contact list.  Anyone not on your list would have the opportunity to leave a message and you could decide to add them or not.  If you have a local cellphone number you can set your landline to forward to your cell.  
If you get Google Voice you don't even have to burn up minutes while you check messages because you can listen to them all online if you want.  I like the feature they have, Global spam filtering, that sends the calls they have identified as spam to your spam folder, like they do your email spam, I think that only works if the caller calls your Google Voice number.

The problem with gadgets like Screen Machine is they're archaic. There's something else on the table here that should be passed around: discrepancy as a safety precaution.  notgiven, connecting your phone to wifi isn't wise, so be very careful if you do that. If I'm following Resident47's comment, and I might not be, they're describing something that would work essentially like a PO box. A unique address which allows for correspondence according to individual needs, but doesn't disclose any information about the final destination or origin of what's being sent.

Viop systems like Google voice -- Google's apps in general -- are great, but there are too many minefields in the cloud, Lone Stranger, you've commented on that quite a bit.

There was a forum thread a few days back regarding a compromised Verizon number. Anyone who wishes to continue this discussion should consider its broader implications, like the ones in THAT thread. It was removed, but I'm sure enough people saw it.