FlexyCore (http://www.flexycore.com) is a French company founded in 2008 by Java experts from Texas Instruments and INRIA (French Research Center). With iSpectrum, they provide a full Java 1.5 compliant solution that allows you to develop in Java and debug NATIVE iPhone/iPod Touch/iPad application using Eclipse IDE.
Note that to compile and obtain an iPhone binary application or an iPhone simulator binary application, you must have installed the iPhone SDK on a MAC OS X (Intel only) and use FlexyCore iSpectrum on this system to be fully compliant with the Apple legacy.
In one click, you install iSpectrum plugin and turn Eclipse into a Java development environment for iPhone. No need to install a JVM, but compiles your Java App to native code with iSpectrum!
iSpectrum provides access to iPhone native APIs (UI, GPS, accelerometers...) in JAVA and enables developers to design powerful iPhone applications in Java. Thanks to its complementary APIs (J2ME like, core Android) an existing J2ME application can be realized and ported quickly.
Note also that iSpectrum directly drives/controls XCode so you can use the iPhone SDK simulator to debug your application from Eclipse!
There is free edition for open source project