I had the opportunity to meet Elio Scotti, President of BEKA USA last week. His company sells radiant cooling/heating "mats" or micro capillary tubes. Aside from the fact that it is an interesting technology, I mention this because they have created a Revit Family for their product.
There is just one family and it is intended for Revit Architecture users for layout/design consideration. It is resizable via grips and it is a representation of its proportions. They are considering the MEP implications for Revit. I'm sure they would be receptive to any suggestions that Revit users offer. If you use this sort of system as part of your "green" goals (that's all of us right?) then be sure to check it out. Either way...check it out!
To download the family look for the CAD Files/Downloads link at the top of the page and choose the Revit link. It will run a script to download the file. Here's an image from part of their slide show presentation available from their site.
This product poses an interesting challenge to Revit because it can technically follow nearly any contoured surface. Making a family that could do that is probably beyond a practical solution at present.