{Apologies for the cross-post with android-developers forum. Haven\'t received any answers there}
I have an interesting design challenge:
I have a fro
How about using a blocking queue, because your description reminds me of a the classic producer-consumer problem from parallel programming class.
http://en.wikipedia.org/wiki/Producer-consumer_problem
Also Java 1.5 seems to have an implementation of the blocking-queue, I can't recall off the top of my head if its available on Android.
http://download.oracle.com/javase/1.5.0/docs/api/java/util/concurrent/BlockingQueue.html
I'd imagine you can setup 2 uni-directional blocking queue's for communication each way. Q1 would have front-end as producer and back-end as consumer. Q2 would have front-end as consumer and back-end as producer.
Also you could use the "Command" design pattern for the communication 'messages'.
http://en.wikipedia.org/wiki/Command_pattern
HTH