We've done some cool things with the Arduino and the BUG. If you had a hankering to do something similar, there are a couple of things to keep in mind. The current released version of the BUG operating system, 1.3, does not have serial java communication built in. If you want to do serial from java, you have a couple of options. You can wait for 1.4 (I want it now!), you can build 1.4 from source -- svn://svn.buglabs.net/bug/trunk (better know what you're doing!), you can hack in a system call (something like Runtime.getRuntime().exec("echo 6 >> /dev/ttymxc/3") debauchery!), or just use c (I really like this little c program, which can be compiled for the arm and even, with some work, turned into a library and used in java via JNI).
The other thing you need to know is how to wire up the Von Hippel to the Arduino. It's pretty simple. You need a couple of capacitors and a 232 or 232A IC. Here is a picture and a sort-of messy diagram.