They're similar, but different. J2ME is a
Java Platform (e.g. JVM) for mobile devices. Jini is protocol and set of APIs for plug and play connectivity. Technically, they have nothing to do with each other. The reality is that I will often bring my mobile device into a new (wireless) network, and want it to interact with that network seamlessly, and that's where bluetooth comes in. We'll definately be seeing bluetooth more on everything from laptops to pagers, where you also find J2ME, rather than on desktops and big iron.
--Mark