Rocket or wood stove for Hydronic radiant floor heat???

Sorry it this has been asked a thousand times before but, it should be since it seems to be such an obvious solution to spreading the heat out more evenly in a larger space than a single bench.  

I just want to heat some water with some copper tubing around a rocket stove exhaust, or even just behind a normal parlor wood stove and send it through some pex tubing in the floor (preferably an earthen floor).  

Is this asking that much?  Shouldn't this be pretty easy?  Why can't I find  info on this?  I'm kind of baffled.  I saw Ernie and Erica talk about it years ago and mention they would release plans for it soon, but I never found those, and can't find much discussion of it.  

Can it be done? is it too difficult ? too dangerous?, impractical in some way?  or if there is something I am just not thinking of that makes this an unfeasible or impractical idea??  I assume pressure issues are the main concern and challenge but it seems like every commercial hot water heater must have some pressure release valves or other safeguards--this must be a fairly easy issue to solve with some readily available parts and a good design, right?  

If anyone can help point me in the right direction on how to accomplish this it would be greatly appreciated.  I've been thinking about it for years, but finally ready to start building, so need to figure out what I'm doing heating-wise.  Also I'd appreciate any recommendations on books to educate myself on hydronic floor heating systems in general--from a DIY perspective

Thanks so much for any insight,

peace and blessings,

Jonathan Wilson

Have a look at one of my old threads...
May be what you need

https://permies.com/t/40/40107/hot-barrel