cordless phone for both VoIP & POTS

[ken]

Until the cost of unlimited cellphone service drops to what is in
Germany (30 euros/month), I'll be keeping my landline. It is time
though for a new cordless phone. I do, however, want such a phone which
does POTS (plain old phone system, what's been in homes since at least
the '50s) and VoIP (i.e., Asterisk on a Raspberry Pi). So it needs to
have two inputs, RJ11 and RJ45. Of course this phone should have
excellent sound quality, what would be expected from a VoIP phone.
Anyone here know of such a phone?

[joeo]

That's called a hybrid or 'dual mode' phone, such as this:
http://www.sophiesystems.com/siemens-gigaset-s675-ip.aspx?gclid=CLe_sradsMYCFQiDaQod4WAO5A

Using a cordless phone on a POTS line does remove one of the best
features of POTS,
the ability to keep working during a local power outage.

You can also use VOIP on an Android phone over WiFi using a VOIP app.
There are various
services that provide both free and commercial VOIP numbers and
services, for use on desktop computers
and Android phones. Google Voice is the most popular, and provides a
free normal phone number and free phone calls.

Another alternative, is to use a voice modem, the FreeSwitch VOIP PBX
program, and an internet connection, to convert ones
incoming POTS line to VOIP. Doing that would allow for example the use
of ones POTS home phone number on an Android
phone while anywhere in the world.

If I was keeping a POTS line for it's safety features (which are better
than VOIP in reliability),
I would probably use the POTS to VOIP/Android approach, and also keep
around a corded POTS phone for emergency plugin use if needed.

VOIP calls are generally now indistinguishable from POTS calls, though
that could change if the new Net Neutrality regulations
effectively outlaw QOS configurations and agreements on backbone
routers.

One of the coolest new VOIP/SmartPhone devices, is the ultra secure
BlackPhone 2:

http://www.cnet.com/news/silent-circle-reveals-secure-blackphone-2-phone-blackphone-tablet/