Very cool! Sure beats the little black notebook I keep in the cabinet above the espresso bar (and that I often fail to update.

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I love the photo fields and I think the best use for the photo field for the coffee is to take a picture of the label on the bag!
I would like to see a space for grinder setting among the key parameters. I know it can be put in the notes section, but it's such an important item for re-dialing the next batch of the same coffee that it should receive more prominence. I realize choosing a format to fit all popular grinders may be difficult, especially something like the Baratza Vario that has two numbers for each setting. Maybe the user could choose between configuring the field for numeric (0-100 by .5) or text entry.
Freeze and thaw dates would be nice. I usually write these on the label of the Mason jars I throw into the freezer, so it would save quite a bit of time to have to enter them only once for a given batch. I can do the calculations in my head (time between roast and freeze, time in freezer, time since thaw), but it would be cool to have the app do that for me.
You might consider having a field for brew method. It looks like the app is currently geared for espresso, but there's no reason it couldn't be used for other methods like drip, pour over, vac pot, French press, etc. Some of the fields might change with the method, of course. One should be able to display the last extractions for all brew methods or the last extraction for all the coffees for a particular brew method.
Finally, I suggest that the brew ratio be settable, so that if you enter any two of the three fields (dose, beverage weight and brew ratio), the app will compute and fill in the missing third value. How nice to be able to enter, for example, 18g for the dose and 66% for the brew ratio and know instantly that you're looking for a beverage weight of about 27g.