ScareBear Trail Companion is an iPhone app that replicates the sounds of bells, clapping, and rocks in a tin can (yes), all of which are supposedly like kryptonite to bears and will scatter them from your path before you even encounter them. Should you happen to come across a bear immune to these charms and wards, ScareBear Trail Companion still has you covered – in an emergency, you can use the app to sound an emulated air horn, which may terrify the creature and send it scurrying away.
There's only three slight weaknesses with this app that I can foresee. First is that it depends on your iPhone having a charge. If your iPhone's battery goes dead in the woods, listen for the spooky soundtrack cues, because that is surely the very instant a bear will charge you from the undergrowth. Second, it takes a lot of concentration on your part to find and launch the app, wait for it to load, and then press the button to make noise; even if you can keep your wits about you when half a ton of teeth and fur is rearing up before you, anything slower than an iPhone 3GS will probably cost you critical seconds. By the time the app launches, you may already be halfway down the bear's esophagus.
Third, and most damaging to the utility of this app, the iPhone's speaker simply isn't all that loud. I've generally found that even at the highest volume, I'll often miss hearing my iPhone's ringtone in a noisy environment – and environments don't come much noisier than a roaring, hungry monster like the one pictured above. Bears may or may not have more sensitive hearing than humans; no one knows for sure, as all attempts to scientifically study these brutal creatures have ended in tragedy, with laboratories leveled to dust upon the bears' inevitable escape from their bonds.
In any case, ScareBear Trail Companion probably isn't going to save your life from a bear. If anything, it'll probably just irritate it and make it angrier. You'd probably do more damage to the bear with your iPhone if you fed it to him. I haven't been able to test ScareBear Trail Companion myself, as there are no bears in New Zealand outside of zoos. As a matter of fact, that's part of why I moved here. Safe at last.