Heater is a tech mod which adds precisely two blocks, the Heater and the Heat Pipe.
The Heater block is a furnace-like block but without any processing slot. Instead, whenever it burns something, it propagates the produced heat to every connected actual furnace, like Furnaces, Blast Furnaces, and Smokers for vanilla Minecraft, but also Haunt Furnaces and Kilns.
In other words, the Heater allows you to centralise the burning process and avoid building complex fuel lines.
On the other hand, the Heat Pipe is a pipe-like block that just extends the reach of a Heater up to 64 blocks.
Not in any particular order.
I am considering whether or not to add redstone logic to the Heater so that it doesn't propagate heat when powered. Until I reach a consensus between me, myself, and yours truly, I'll implement nothing.
I don't quite like the Heat Pipe's texture, but I haven't yet been able to do better. However, I have already spent too many afternoons drawing ugly pixelled textures for now and the foreseeable future, so that's on hold. I guess the same goes for Heater block, although I don't dislike it as much.
Finally, since the Heater and the Heat Pipe are both copper-based blocks, I should add some oxidation logic to them, but again, textures, see above.