Excelsior JET, which is actually Version 6.5 of its JVM, enables developers to compile an Eclipse RCP application to a native code executable and distribute it without the original class/jar files.
By distributing without the jar files, your application is secured against reverse engineering and tampering with OSGi bundles. Java decompilers become useless to hackers because they can't see the classes inside the installations.
Want more security?
It compiles platform neutral Java code down to native CPU instructions. The resulting binary executable is as hard to reverse engineer or tamper with as if the application was written in C++.
Beta code is already available, although this version just has a command line interface. Future code releases will include a GUI.
Versions are available under both Linux and Windows, and it works with Update 7 of Java SE 6 as well as J2SE Version 15.
UPDATE: I was curious about the August 1 date of this release, and Dmitri Leskov was kind enough to fill me in.
Turns out there is a total eclipse of the Sun happening right now, today, over the city of Novosibirsk, where Excelsior is located. You can view it through the NASA Web site.