I'd include somewhere to enter weather information other than the notes section - could track rainfall (per event, per time period), drought conditions, major weather events (storms with heavy rain, hail, strong winds - all of which can devastate a vegetable garden), last/late spring frost, first frost.
Also a pest section - insect, plant(s) affected, how the person treated (or did not treat); fungus, plant(s) affected, how the person treated (or did not treat). Same for birds and small mammals (children?)
It may be helpful to have a place to record where the seeds (or seedlings) where purchased and price paid.
If you're going to include flower gardens, then you could put in things like: plants acquired/where purchased/hardiness zones, along with the usual varietal information. You could also have a place to record plants that died/did poorly and those that did well. I think the place purchased could be very helpful since this is a local app.