To all developers:

there is a quite easy app I would love to see:

For most countries there is a clear relationship between zip codes and city names and maybe even streets (i.e. in the UK).

I would love an app that would lookup the missing parts when I enter a street and/or zip.

Since data plans are still very expensive in Germany I would prefer a local app that looks up the data in a DB on my device, but over-the-air it should be easier.