I assume by "micro bore" you mean the standard 1/2" or 3/4" copper water pipes?
What you describe is possible, and in my imagination could even be fully automated with thermostat if you designed it right.
You are also squarely in the realm of BOOMSQUISH. Which is Paul's way of saying you probably shouldn't try this unless you are a water/heat/steam professional because by the time you notice the BOOM you will already have been SQUISHed.
I do have a few recommendations for you if you haven't seen these resources already:
1) Check out
http://www.richsoil.com/rocket-stove-mass-heater.jsp specifically Paul's two podcasts linked near the bottom:
http://www.richsoil.com/permaculture/182-rocket-mass-heaters-permaculture-podcast-019/
http://www.richsoil.com/permaculture/613-pocast-098-hot-water/
2) I also highly recommend all 4 of the new Wood Burning Stove 2.0 DVDs, but if all 4 are out of the question specifically the BOOMSQUISH DVD (which, you should know, does not show you HOW to do this but does go over what you need to think about in detail and shows a system that works).
http://www.woodburningstoves2.com/
3) Pick up E&E's book
http://www.scubbly.com/store/ernieanderica/
4) Build an RMH from one of E&E's approved plans
http://www.scubbly.com/store/ernieanderica/ for experience, and to ensure you have a design which will work.
Perhaps you've already done all of this, if so I apologize.
You may find that with an RMH installed that piping of heat is just unnecessary, or that it wouldn't be worth the tinkering. At the very least you will have built a system that you know will work and can take that experience away with you before you start to innovate.
The most important take-away is something you probably already know and just haven't thought about. Ernie and Erica don't do this. The primary innovators and researchers in this space choose not to mix water and RMH technology. I understand that part of that stems from what I've already said, the danger potential is real, especially for a backyard innovator.