Android :: Remote Service Returning Value From Http Transaction

I've been researching how to best implement a service which performs a network transaction and returns data to the caller.

Clearly, this needs to happen on its own thread which means some form of async response. I can see at least three ways of doing this--some more complex than others. In the descriptions below, C is the caller, S is the service.

1) C wraps a Handler in a Messenger object, adds this to an Intent. C then calls startService with this intent. S extends IntentService which runs the Intents received in a worker thread. S then sends a message to C via the Messenger. This has the benefit of not requiring any of the async binding process or making an IDL interface that needs to be compiled into C. This seems to be the closes to a Handler-based response mechanism of Local Services.

2) C binds to S and then uses AsyncTask<> to make a blocking call to S. S performs the network transaction and returns the data in the return value or an out parameter. This requires the async binding process, but does not require a callback function since the inter- thread communications is handled by AsyncTask<> and the worker thread is in C's context.

3) Make the function called in S be completely asynchronous. S defines two interfaces: IMyService and IMyServiceCallback. S implements IMyService.Stub. C implements IMyServiceCallback.Stub. C binds to S then calls S via IMyService, passing its IMyServiceCallback binder. S spins up a worker thread and returns immediately. S then calls the callback when it has completed the network transaction.

I am asking for advice on which methods are most appropriate. I do not need the the service running constantly, only when the web transaction is required. C does not use S all the time--definitely don't want to bind during C's onCreate. However, I would like the time from when C determines it needs to use S to getting the results back to be as quick as possible (i.e. adding minimal latency to the already latent network access).

Is there any preference to having the worker thread in C or in S? Are there any significant problems with option 1?