Zivix, known mostly for its Jamstik MIDI guitar, recently introduced AirJamz ($50), a Bluetooth “guitar pick.” Using a free app, the pick lets users play air guitar like never before, as their strumming motions in the air are turned into music and sounds within the app. The app comes with 25 free downloadable tracks, and a few extra tracks can be purchased, too. You can switch through available instruments for each song within the app,…