Gadget reseller Gazelle lets you sell your iPhone from your iPhone (video)

Just in time for the iPhone 5 launch, the electronics reseller Gazelle has launched a new iOS app that will make it dead simple for you to sell your existing iPhone.

Gadget resellers typically receive a flood of used iPhones and other mobile devices once a new iPhone is released. Now, with its iOS app, Gazelle has made selling your older devices as easy as downloading a new iPhone game.

As Gazelle chief gadget officer Anthony Scarsella demonstrates below, the app automatically detects the iOS device you’re running and asks you just three easy questions about your device’s condition. Once you confirm the sale, Gazelle emails you a prepaid shipping label that you can slap on a box and then drop off at a package shipping store or kiosk. For high-end items, the company also ships you a box with a shipping label to make the process simpler (although that takes longer than providing your own box).

Once you choose to sell your device, the price Gazelle gives you is locked-in for 30 days. The company also offers a variety of payment options, including PayPal, check, Amazon gift cards, or you can donate your proceeds to charity.

Scarsella says the company is expecting more iPhone 3GS units this year, likely because the two-year AT&T contract for those customers will be up.

Check out a video demonstration of the Gazelle iOS app below. (Excuse the sound and wonky camera work; I shot this at a very busy industry event in Manhattan last night.)