I am a java programmer and have written bluetooth applications for phones.
It is possible for a java program to send itself, or a modified version of its self to another telephone over bluetooth (If less than 7 meters away).
However, the recipient is asked weather they want to install the application. Even, if you install the application and run it, no harm can be done to your phone and your privacy can not be invaded.
Java is designed with security in mind. A Java application can not dial numbers nor can it access you personal information(phone numbers, messages, pictures etc.) Your phone will always ask you if you want to permit the java application to:
* Contact another phone via bluetooth
* Dowload or upload information to the Web
*Take a photo with you camera.
I like the idea of writing a java phone application that people will want to send to their friends, but it can only proliferate if phone users actually permit it to.