Nice work, it's very impressive and it's something I'd definitely consider adding to my enlarger (a LPL 4500).

However, FWIW, I am in agreement with Ken and PKM, I have no interest in giving up my f/stop timer, even if the functionality were on a phone app.

For one thing, I don't want to worry that some future phone or even OS update for the same phone may or may not be compatible with my enlarger.
For example, google IOS 6 and bluetooth...