like push registry in J2ME which enables apps to set themselves up to be launched automatically, without user initiation. Activations could be inbound connections like: message-based (such as SMS), stream-based (such as TCP socket) or packet-based (such as datagrams).
It's more that they are system events, not network events. So, you can wake up on an SMS, or a low-battery condition, or getting near some GPS-based location. Networking, however, is not handled this way -- more like JavaSE than JavaME.