Well I had to find out about this and if it really worked, so I bought one and here is a little video clip of how it works.
I apologise for the quality of the clip because I do this so infrequently that I forget how to use the imovie function on my laptop - still it gives you a demonstration on how it works. By the way, I am almost just hovering the iron over the mark, so I would think that you could just put the fabric near anything that produces heat and it would make the mark disappear. See what you think.
FYI - I have only tried it on this piece of fabric, so needless to say you would need to test it on a scrap of fabric first just in case it reacts differently on different fabric types. This is not a direct endorsement of this product - I read about it and thought it a good idea and just wanted to give it a go. I purchased my black pen from Amazon with 3 refills for just over £10. A recent search showed that other colours are available.
Catch you later...............