This app was mentioned in 1 comment, with an average of 3.00 upvotes
CoffeeLazy is pretty handy as an all-in-one calculator/timer/log.
I like BaristaMe for the ratios of various espresso drinks, but I never use the brew functionality.
Mr. Barista looks interesting, but haven't tried it yet.
As a general tasting app, Angel's Cup works well, and it integrates with their subscription service.
There's also a few espresso timers which start the stopwatch when the machine vibrates, but I've got a manual machine so I haven't explored those.