Any ideas for useful(not for fun) Android applications?

I am studying in Android programming and would like to develop an useful Android application for my project, but I still could't get any good ideas after searching on the i开发者_JS百科nternet. Any suggestions that an app is useful in our dailylife even achieve the society such as about public health, education, security?

what about an intelligent mobile health care system you can write an android app instead of the j2me app mentioned here.

An application that detects if you are in trouble (being kipnapped, etc) using different sensors to detect struggling, shouts... and then call the police and start ringing at a very loud volume.