I have recently gone on a shop hop. In one store they
demo-ed a pen. As they wrote on the fabric, it just looked like a pen. To erase the marks you just iron them and they disappear. They told us that the pen is heat sensitive, so it shouldn't be left laying where it is hot, or in the sun.
Haven't tried it yet, but am looking forward to using it.
The pen is made by Pilot. Name on it is FRI X ION. Cost was $2.95.