That being said, when Guitar Hero came out for the Wii I got a copy, realized that they had captured some of the 'feel' you get when you are playing for real (my nominal instrument is trombone but not a lot of call for that :-) and found it fun. So I took the open source bluetooth driver for the Wiimote and created an app that basically let you play a song and pace it with the 'strumming'. Its great for kidding around but not as satisfying as having to work the frets etc.
So here we have a guitar that can do a bit of both, play 'fake' where only the correct notes play, or play 'real' where all notes play. Cool idea.
The price though. Ouch. Lets look at that for a minute. After they build their first batch, guitars will be $450 each. And they need an iPhone to work at all. So a used iPhone is maybe $100 so you are looking at $550 all up. A student guitar is $60 and lessons are like $100/month so call it 5 months of lessons.
I'm guessing that if you don't even know if you like to play the guitar its going to be too much of a 'risk' to invest in it. That will greatly limit the market. If they are successful I hope they come out with a dedicated built in compute unit.