I am contemplating a full-blown whiteboard/pinboard for it. Because my garden is small but intense, and while I keep a diary, it's a bit of a mess. (A bit.)

And yes, I'd kind of like an app that could at least tell me what I've grown and who I bought the seeds from, and how they grew in my area and where in the garden I planted them...but I think that my ambitions highly outstrip the capabilities of any app that could be created (unless i made it specifically for myself).