Smule — of Sonic Lighter fame — launched their second app over the weekend, Sonic Boom. As you can probably imagine, it turns your iPhone into a virtual firecracker that can be lit, either with your finger (as a virtual match that you actually have to strike to ignite) or a second iPhone running Sonic Lighter.

Sonic Boom, like its sister app, is more gimmicky than anything else and is hardly feature intensive. You can change the size of the firecracker or the fuse, slow down the explosion, and wrap your stick with a picture from your camera roll. You can also rummage through the debris afterward, however the graphics are nothing to phone home about and are on par with what you would expect from a 99¢ app.

Where Sonic Boom really shines is the real-time display of other users around the globe. Smule claims they have registered ~7,400 explosions in the app’s first 36 hours and during my usage, I averaged a fair number (5-7) of explosions every couple of seconds, most of them culminating around the USA and Europe.

Curiously enough, you can cause the explosion to “break” your screen. It seems to be more random than anything, but obviously the bigger your stick, the more likely your chances. You can check your stats to see how often you’ve done so, as well as how many times you have lit a firecracker in general.

All in all, if you’re looking for a way to have some momentary fun without losing fingers or something to accompany your friend’s Sonic Lighter purchase, this is it.

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Today, Smule released a really cool (or hot, if you want to be go that route) app for the iPhone called Sonic Lighter.

Sonic Lighter is an iPhone-only app (sorry iPod touch users), that makes use of the accelerometer and sound to affect the flame it shows. Simply flick the flints on the screen to light the flame and then turn the iPhone from side to side to see how the flame reacts. Turn it too far and it will digitally burn the side of the screen…how 21st century. You can even run your finger through the flame and it will react accordingly. To put the flame out you just blow in to the microphone and it puts it right out.

What I think is infinitely cooler, though, is its ability to ignite other iPhones. The flame gives off a faint crackling sound through the iPhone’s speaker, so when you put your phone up next to another iPhone (with Sonic Lighter installed), it will light the flame in the app. It does this through the receiving iPhone’s mic by picking up the crackling noise to detect proximity of the flaming iPhone.

There’s also a world map of everyone who has set their iPhone ablaze. San Francisco and New York appear to have burned to the ground.

Sonic Lighter is more of an experiment in sound and physics than an actual featured-laden application that you can do a lot with. So in that sense, it is a tad gimmicky considering you have to pay for it. Though, for only 99 cents, I can definitely say it’s worth it for a quick entertainment fix…especially if you can get some other friends to buy it. Then you can all sit around, light each other’s flames and sit in a dark room listening to Free Bird. Or not.

Here’s a quick YouTube video of the app in action.

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• Mobile Q4: All Eyes Were on Android, 4G and the Rising Tablet Tide
• Report: A Mobile Video Market Overview
• In Q3, the Tablet and 4G Were the Big Stories