There is a limitation on how many backers for each offer so if this looks interesting to you. Head over to their Kickstarter page and take a look. There will also be some other bonuses if they reach their new stretch goals as can get seen here.
So it means that there is many apps that it would not be useful for...
Which brings me to the next issue regarding developers.
They are asking for developers that have interest in making apps compatible.
Guess it would be a question of maybe making some rotaries in the app bigger or adding a new rotary control or two?
Tuna Knobs Kickstarter page: