I thought about building a system for charity/thrift stores that let them scan in the ISBN of every book donated. I'd run a central database so you could search

I thought about building a system for charity/thrift stores that let them scan in the ISBN of every book donated. I'd run a central database so you could search for a book and see where it's in stock in your city. Likewise could set alerts for when a given book is donated - and helps store to price books appropriately. I decided it was unlikely that people would find the books they wanted in their city so it's pointless. Didn't see this angle though - catching the odd winner that goes unnoticed.