I agree with Will Fly that every guitar tunes differently but, reading the blurd, it appears that the contraption can deal with that by way of a smart phone (whatever one of those is) app.

Electric tuners are a great way of making sure that everyone in a band/ session is tuned to the same frequency but I suspect that this device will get whole heartedly confused if someone else is playing/tuning in the vicinity. How do you make an accordionist play? Start tuning your guitar!