Since deciding to turn part time hobby development for myself into a part time hobby that produces stuff others might actually buy, I've been looking through my list of ideas and trying to figure out some sort of progression through them. This involves evaluating which ideas are practical for me to pursue (I've got some pretty out-there items in my list which I think would be awesome that I just don't have the time or expertise to attempt at this point) and which might actually be appealing to others.
The ideas that I've gone with so far have mostly been things that scratch my own itches or those of people I know. I guess this sort of thing would fall into the "passion project" bucket. The problem is that most of what is interesting to me is probably not interesting to the rest of the world, and things that I need tend to have pretty small niche appeal.
It's also been a process of filtering my list through what's already available. For example one of the early items on my list was a simple database app for handling membership info for the karate club which I belong to (and at the time, was secretary of). It was quite easy to do it with a simple spreadsheet, but I figured that it would be much easier to have a mobile app since then it could have access to the camera for member photos, and my phone or ipad was usually with me (I've been meaning to put together a post on video coaching with the ipad for a while). Definitely a case of scratching my own itch, but there are clubs everywhere so I thought it could be worthwhile.
I did some basic research into the concept and didn't find anything compelling for club membership. Either they didn't allow for custom information (e.g. current belt, grading dates etc) or they were a front end for a subscription back end, which just wasn't worth it. On that basis I figured it'd probably be worth investing some time into and could probably promote to other clubs if it turned out to be any good.
Fast forward a year or so and I'd moved towns and so was less directly associated with the club, so someone else had picked up the secretary role, and so my motivation to follow through with the project had dropped off.
Coincidentally I was looking into consumer database apps for one of the classes I was teaching, and ran into two bits of software that would have solved my problems completely: Tap Forms (Mac, iPhone, iPad - paid upfront) and Objectality (iOS - free with pro features as IAP). Both allow you to create lightweight form-driven databases, sort and run custom queries, and import and export data. With some fairly basic work, I set up exactly what I wanted for the club database, only a year or two too late to use it for myself :) The trouble of recommending apps like these to the new secretary is they're fine for the level of nerdery that I'm comfortable with but I'd be hesitant to do the same for someone less comfortable with fiddling with apps and data.
For what it's worth, Objectality is actually really good for an essentially free app (from what I can tell I wouldn't need any of the pro features) with some pretty average documentation and a couple of minor UX warts.