[sneusse]

Not quite useless but more like a one shot use: I spent some days building a flight/train route optimizer for traveling to N cities, staying at least M days while minimizing travel costs for a single journey in 2018. Was fun to build and we payed like 200 € for one month of traveling in Europe :)

[yscodes]

Sounds useful to me, something you could make into a webapp! Anything that saves people money is likely to succeed.