As an exercise I am planning on building a new open source blockchain/currency completely from scratch in Java.
Rather than be one of the many clones of Bitcoin, this will be something new.
My question to you guys is: which features do you think the blockchain/currency should support?
You could create a coin that's based on public areas. I'm not sure if this is done yet, but maybe something to pay for parking garages? When in a downtown area, at least where I live, there are some annoying things about the parking situation, and many people don't keep quarters on them. They're basically screwed if they want to park or they have to find somewhere else to park. Maybe if there's some solution to that issue in a coin that's rooted in your phone itself, it could be a potential solution.
I get ideas from thinking about how an every-day situation can be sped up/improved. Maybe this advice can help you out, pm me if you want some other ideas too.