At what size does an accessory become the main thing and the mobile device the accessory? I don't know, but the gTar iPhone "companion" on Kickstarter certainly begs that question. It's the size of a guitar, because it is a guitar…kind of. The strings don't play music, but instead transmit data to the iPhone that's docked in the gTar itself, which then produces the sound. The whole thing is made to be a tool to learn to play the guitar, so the idea is that you play by using the tabs on the screen and the LEDs that light up on the guitar itself to get the grips right, and then you can advance through different modes where the iPhone will help you less and less with blocking out wrong notes, until you're eventually playing on your own.
I have no musical talents whatsoever, but I still had a synthesizer for several years where I basically only ever used the learning mode to teach me how to play songs in a very similar fashion to this. I eventually started using it with my iPad, which can handle MIDI input like that through USB. Point being, those kind of learning modes are truly useful for learning an instrument, and seeing something that both brings that to guitars and uses a mobile device as its brains at the same time is really something.
This is no simple plastic slap-on product though, so the prices start at $399 (limit amount, then $450). That gets you the gTar, bag, strap, charger for the 5000mAh internal battery, USB cable, replacement strings, SmartPicks, and a headphone adapter. Pledging $599 gets you a very neat reward that includes a "song selection", which is essentially where you get to pick a song to be included in the app – assuming that the licensing is possible. $999 is the top of the line pledge level, where you get a custom painted gTar as well as the song selection.
With no knowledge of whether the next iPhone will work however, this might be a shortlived accessory. This is a Kickstarter project though, and one that has already raised twice its $100,000 goal in just a couple of days, so it's not inconceivable that there will be changes made to the design before it gets manufactured that will incorporate a snap-in system to make it work with more devices. Perhaps the most obvious solution would be to connect the device wirelessly and use just a plastic adapter for the physical connection, which would open it up for more platforms than just iOS as well. Time will tell.
I'm sure there are plenty of people out there who will have comments about this way of learning an instrument, but personally I just think it's a cool way to bridge old technology with new.[Kickstarter]