This is cool! I like it more than TAC explosives. The heat limit and minimum safe distance is a nice touch. If I can make a suggestion, maybe include a readout of how far away you are (or your focused vessel is) from the explosives.
This is actually from yesterday, but here's a story: http://www.reddit.com/r/KerbalSpaceProgram/comments/2jkgd2/it_was_supposed_to_be_a_simple_mun_landing/