Paul,
I agree with you on the fact that most of options are Windows based, which seems to be true of most things HA, not just xAP, take a look at all of the new product announcements on CocoonTech... Which is precisely the reason that I decided to write the stuff that I'm doing in Ruby. Java would have been cross platform as well, but I've been coding in Java for the past 12 years and I'm sick of it.
If you're interested in xAP I'm working on several xAP applications. So far I've written a xAP library for Ruby, a xAP connector for the NetCallerID, a xAP connector for Festival TTS (text to speech) and now I'm working on a xAP connector for the TI103. I haven't publically released any of them yet because I haven't had time to document them. I've been running the first three in my house for about the last 9 months or so. If there is interest I could probably spend a little time writing some documentation and cleaning everything up and making it more user friendly.
Another reason that I haven't released anything is that there is a piece of middleware missing, which is the controller or message processor. Right now I've just got a quick and dirty little app that checks for incoming caller id messages and creates speech messages. I'm still working on a design for a message processor, I'm thinking that I want a rules engine and neural net based processor, but that will be some more work.
Mick