Last week I decided to have a go at building a location based app, using native APIs for both android and iphone, but using a webview to display the content. It came together pretty well I think, still waiting for the ios app store to approve or reject the app. The app sends messages to anyone within 100 metres of you:

http://herenow.nolanconsul.com/

I blogged a bit about it here:

http://bennolan.com/2014/05/27/herenow-retrospective.html