Surprisingly capable of running solely off of power from a connected iPad -- assuming that you're willing to self-supply the USB to Dock Connector adapter from the $29 iPad Camera Connection Kit -- Samson's new Carbon 49 ($125) is a complete MIDI keyboard solution for use with GarageBand, other iOS apps, and computer software. Designed to hold an iPad in a dedicated slot behind the 49-key, velocity-sensitive synthesizer keyboard, this accessory uses…