How to Build a “Spy Camera” App for an Android Phone with Ruby and Sinatra
It's been a great year for Ruby on Android, but no one knows it. You can start writing Ruby apps for Android devices TODAY. You don't need to install any SDK, you don't need to install some giant Eclipse IDE, and you certainly don't need to write any Java.
In Turn your Android Phone Into a Remote Spy Camera with Ruby in 15 Minutes, Mike Leone demonstrates how to use Ruby, Sinatra and Scripting Layer for Android (SL4A) to build and deploy a phone-hosted "spy camera" Web service.
Even if you don't want to build a "spy camera", Mike's walkthrough is a must-read if building Web services in Ruby that can run directly on the Android platform is of interest to you.