Despite all the information about avalanche beacons on BeaconReviews.com, when you really get down to it, avalanche transceivers do only two things:

1. They transmit a beep.
2. They help you find a beeping transceiver.

By contrast, a "smart" phone can do, well, pretty much anything that involves data transmission and digital processing.

So why can't my phone also serve as an avalanche beacon?

First and foremost, although a phone's antenna can receive cell phone, Wi-Fi, Bluetooth, and GPS frequencies, it can't transmit or receive on the 457 kHz avalanche transceiver frequency. The very long wave of this frequency allows it to penetrate snow without any signal loss, but it also makes it difficult to create antennas that are short enough to fit inside a phone.

And since a cell phone can't transmit or receive on the existing avalanche transceiver frequency, any cell phone app that attempts to replace an avalanche transceiver will work only if everyone in your party has the same app. That's a problem. Another problem is that cell phone batteries don't last very long. Certainly nothing like the minimum of 200 hours transmitting followed by one hour of searching which is required for traditional transceivers.

The next problem is using the touch screen with some combination of numb and trembling fingers in cold, wet, snowing, windy (or blindingly sunny) weather. It's difficult enough to place a phone call in this weather let alone use it as life-saving rescue gear.

And even if you are willing to accept the above limitations, understand that neither of the currently available apps provide any directional or distance information—only signal strength. In other words, the apps can't tell you whether you should go left or right, only whether the victim's signal is getting stronger or weaker.

Here's a look at a few apps that are currently available (we're hoping the list doesn't grow...).

iSis

Another phone-based app, iSis, has been released. iSis has a creative approach. First, it can use your trajectory (presumably a fall) to send text alerts to your predesignated friends or to a rescue group (e.g., the ski patrol). The search is done using a combination of GPS, Wi-Fi (up to 1000 meters), and Bluetooth (up to 45 meters).

Their website states, "Attention, iSis is not a magic cape of invincibility. The application neither replaces thorough preparation for your mountain excursions nor the adherence to "best practice" and safety rules of the mountain." We agree it isn't a magic cape of invincibility and it doesn't adhere to the safety rules. Let's hope its name, ISIS, scares people away.

Snøg

Snøg(for Android phones) is free. It uses Wi-Fi signals to transmit and search. Snøg's transmit mode simply configures your phone to serve as a Wi-Fi Hotspot. Then its search mode looks for Wi-Fi transmitters, just like when you're trying to connect to a Wi-Fi network.

Snøg can search for your "buddies" whom you register beforehand or for all networks. Instead of displaying a list of nearby networks with signal strengths of Fair, Good, Excellent, etc., Snøg displays a bar graph for signal strength. Each bar is topped by a number, but this is not the intuitive distance estimate of a real avalanche beacon. Within about a meter of my office Wi-Fi antenna, the bar read 60, but a Wi-Fi network in a neighbor's was in the high 20s. (An avalanche beacon searching at those distances would have read about 1 and 35, respectively.) When I was immediately on top of my Wi-Fi antenna the signal maxed out at about 90, but constant fluctuations of ±10 were typical. This warning from the user manual could provide some of the explanation:

"Do not tightly cover the Wi-Fi chipset spot it greatly affects the receiving and sending properties of your phone. Every phone which supports Wi-Fi has a Wi-Fi chipset this chipset is located somewhere at the edge or in the middle of the phone. That can be for example your hands while searching. Check where your phone has its chipset by testing with Snøg avalanche buddy." [Typos been corrected, but the syntax is original.]

In a June 2013 on-line comment, Snøg referenced a possible upcoming paid version with Bluetooth and GPS (they may want to read about SnoWhere's Bluetooth challenges).

SnoWhere

SnoWhere (for iPhones) costs $9.99. It uses Bluetooth to transmit and receive GPS information. They've had significant problems with SnoWhere's reliance on Bluetooth transmission of GPS location information:

• GPS signal acquisition underneath snow. A high-sensitivity GPS receiver with an antenna optimized for GPS signal reception can indeed acquire GPS signals underneath snow. But phones typically lack the very latest in GPS chips, and their antennas are optimized for cell phone networks, not GPS satellites. SnoWhere claims, "SnoWhere's ability to identify your location is dependent on variable GPS accuracy. In our tests, the best GPS accuracy was ±5m on iPhones 4 & 4S and ±10m on iPhones 3G & 3GS. Signal strength display helps determine the distance between iPhones with greater accuracy than GPS." Even setting aside the uncertain rigor of these tests (and the uncertain meaning of the final sentence quoted above), running the math, the very best scenario requires that a searcher probe either 845 or 3,382 square feet (iPhone 4 and 3G, respectively). And who knows how much that degrades under whatever more demanding scenarios that SnoWhere did not test.
• Bluetooth transmission underneath snow and over long distances. The iPhone 4S cited by SnoWhere has Bluetooth 4.0 and the earlier versions listed as compatible with SnoWhere have Bluetooth 2.x—yet SnoWhere only vaguely claims that, "SnoWhere has a range of 40m and has been tested in depths up to 2m." without specifying which model was tested. Somewhat anecdotally, my Droid Incredible has Bluetooth 2.1 with a headset range of only a few meters before static overwhelms the voice quality.
• The useful aerial extent might be minimal. If SnoWhere's vague claim of a 40 meter range does indeed degrade under certain conditions, and if SnoWhere's 10 meter accuracy claim for the iPhone 3GS also degrades under certain conditions, the span over which SnoWhere provides any useful information might approach zero (e.g., 25 meter Bluetooth range coupled with 20 meter GPS accuracy).
• Wi-Fi interference. Remember to turn off Wi-Fi beforehand "for best performance" (such as it is).
• Phone call interference. The following passage implies that if a phone call is randomly received during the search, then SnoWhere will shut down entirely: "SnoWhere also remembers when you might forget by restarting automatically after phone call interruptions to keep you transmitting, so your friends can find you. You'll always know that SnoWhere is running by its reassuring ping."

Conclusion

Overall, these apps would make nice school projects, but they are woefully inadequate for their intended lifesaving roles. Also note that the SnoWhere Facebook page shows the last update on January 28, 2013 without any references to the iPhone 5 that was released in September 2012 or the iPhone 5C and 5S which were released in September 2013. Perhaps the only good news in all of this is that SnoWhere is no longer trying to market this app actively even though it remains available on the iTunes store. More grandly, despite concerns that legal liability will stifle innovation, clearly these developers are not afraid to market purported lifesaving products that are almost inherently incapable of saving any lives.