At the JavaOne 1998 conference, Sun gave out rings like this one. It's embedded with an iButton chip containing a Java Virtual Machine. Based on the 1-Wire device communications bus system, IButtons can act as a token for access control, e-cash, data logging etc. 1-Wire systems are still in common use and someone is selling Java Rings in many sizes for $24 on eBay. "JAVA RING: RARE! Sun Microsystems JAVA ONE Promo"