The problem with having 8 buttons is that you will be stuck to one "key".So for example if you have the notes Do, Re, Mi, Fa, Sol, La, Si, Do you will be stuck playing in Cmajor (you could also play in Am and in a couple of different modes, but that's a different story...).If you want to play the "Happy birthday" song, and you want to start with Do, it means you need to play it in the key of Fa Major.This means you would need to use the notes:Do, Re, Mi, Fa, Sol, La, Sib, Do. <--- Notice the Si is FLAT!
What is not easy is making it kinaestheticly useable. Once the project is complete it should have a use. In this case it should enable the users to create music, so the instrument needs to be playable and have some kind of visual and tactile appeal and ease of use once completed
I think the guy said he wanted it wireless