That's what I'm thinking now when I think about trying to find some sort of sweet spot for mobile development. I'd like to think a little bigger, but as an independant developer, I can't practically expect to develop any huge all encompassing system for mobile phones, can I? I mean, I can come up with a zillion ideas of things that people might want to do, but I have no chance at all of actually implementing them.
So right now, what's on my mind is "Things to do while you're waiting." Which makes sense as a sure-fire need for mobile users. I don't know how to guage the American market much because people spend sooo much time in their cars and not for the most part urban commuters like those in Europe. But even Americans end up being stuck waiting for Dentists.
I also have a twist on this - I want the apps to be "downloadable/usable offline" so that I don't have to be connected to the internet. For two reasons: 1) GRPS in many markets is still really expensive and 2) Connectivity isn't guaranteed. Look at everyone in the Metro. Every person on the Madrid Metro has a mobile phone, but most people are staring at the ceiling or at their feet. These are all potential customers for apps they could grab while in the fresh air and bring down with them into the dungeon while commuting.
So what to develop? There's lots of ideas. Games fit into this category - including my favorite the crossword. Chatting is out - though composing your thoughts in an offline weblogger would be good.. eBooks, eMagazines or an offline news aggregator would be killer. Probably some more - I've got an outline of this stuff.
Here's my first thought: A lot of this exists, but is all over the place. An opportunity is to create a web/wap site where it's a bit more organized. Maybe this already exists... but if it does, I don't know about it which means they're not doing enough marketing. A second thought is that a lot of this doesn't exist and there's opportunities there as a developer, but you have to find a good business model. You have to sell A LOT of widgets at $6 a widget to make money.
The cool thing is that this is all just starting... again, I think we need to look at Japan and see what they're doing there as a good idea of what's coming.