Hi, love the show!
I wondered if you could build a good quality chromatic tuner for instruments such as guitars. It doesn't have to be small.
There are a lot on the market but they have the equivalent of an iphone's circuit board in them. Mechanical ones do exist too and are incredible but cost a limb.
I just thought that something relating to music can make for a different show ( I couldn't choose a category in your form 
)
Anyway I'm sure you could pull this off within a couple days
Regards from across the pond.
Will
