Introduced in late 2010 and still quite unique within the world of iPhone accessories, Cobra’s PhoneLynx ($60, aka BT 215) is a brilliant invention: a Bluetooth bridge between one or two iPhones and a landline telephone. Powered by its own included wall adapter, the black matte plastic PhoneLynx sits on a table besides whichever traditional phone you choose, connecting to that phone using a conventional RJ11 phone cable — included with the phone, rather than PhoneLynx. When you want to make a phone call, you can just pick up the landline phone and do so; when a call comes into your iPhone, the landline phone rings, feats that sound simple but are tricky for companies to accomplish. Better yet, PhoneLynx can be paired with two iPhones at once, enabling each iPhone’s calls to ring through to the same landline phone.

If the value of this accessory isn’t already obvious, that’s probably because you haven’t owned a wireless home phone system: paired with DECT or other wireless handsets, PhoneLynx is the missing link that can share a single cellular phone line with an entire house full of people. And the specifics of the way the accessory works are almost uniformly impressive.
Once you’ve paired PhoneLynx with your iPhone, picking up the landline phone leads to an actual dialtone and the ability to dial out: the number you enter is transferred correctly to the iPhone. Alternately, you can dial using the iPhone and switch over to the landline phone as desired; obviously, only one iPhone can make outgoing calls using PhoneLynx-connected landline phones at a time. If you’re using a wireless system, calls that come into either iPhone ring across all of the wirelessly connected phones pretty much just as you’d expect: there’s only a small 1- or 1.5-ring delay when PhoneLynx has to switch between iPhones to handle incoming calls, and sometimes a brief continued ring after the phone’s been answered. Depending on how many rings your phone has before it goes to voicemail, this may or may not be an issue for you.
The ring delays and PhoneLynx’s approach to iPhone pairing are the only signs that the Bluetooth chip used in BT 215 isn’t of the very latest variety. To pair, you’re required to hold down one of two illuminated buttons on PhoneLynx’s top, then manually enter a four-digit pin code into each of the two iPhones.
Once that’s done, lights on the unit flash blue to let you know pairing is active. If the link between your iPhone and PhoneLynx is broken—say, when you’ve left the house and then returned—you can manually press the button corresponding to your phone to re-pair, or just wait and let it happen automatically. Most of the time, the automatic re-pairing works. Ideally, Cobra would update BT 215 with newer Bluetooth chips for faster and easier pairing, but even if it did, only newer iPhones would support the improvements.
Sonically, the experience of using PhoneLynx will depend almost entirely on the quality of the landline phone you pair with it. Callers told us that we sounded more or less identical through the integrated microphone in the iPhone 4 as we did when using a landline wireless DECT phone with PhoneLynx.